Open Geospatial Consortium |
Submission Date: <yyyy-mm-dd> |
Approval Date: <yyyy-mm-dd> |
Publication Date: <yyyy-mm-dd> |
External identifier of this OGC® document: http://www.opengis.net/doc/IS/geosparql/1.1 |
Internal reference number of this OGC® document: 22-047 |
Version: 1.1 |
Category: OGC® Implementation Specification |
Editors: Nicholas J. Car, Timo Homburg, Matthew Perry, John Herring, Frans Knibbe, Simon J.D. Cox, Joseph Abhayaratna and Mathias Bonduel |
Contributors: Paul J. Cripps, Krzysztof Janowicz |
OGC GeoSPARQL - A Geographic Query Language for RDF Data |
Copyright notice |
Copyright © 2021 Open Geospatial Consortium |
To obtain additional rights of use, visit http://www.opengeospatial.org/legal/ |
Warning |
This document is not an OGC standard. This document is distributed for review and comment. This document is subject to change without notice and may not be referred to as an OGC Standard
Document type: OGC® Standard |
Document subtype: Encoding |
Document stage: Draft |
Document language: English |
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i. Preface
The OGC GeoSPARQL Standard defines:
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A formal profile;
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this document;
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A core RDF/OWL ontology for geographic information representation;
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A set of SPARQL extension functions;
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A Functions & Rules vocabulary, derived from the ontology;
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A Simple Features geometry types vocabulary;
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SHACL shapes for RDF data validation.
This document authoritatively defines many of the Standard’s elements, including the ontology classes and properties, SPARQL functions, and function and rule vocabulary concepts. Complete descriptions of the Standard’s parts and their roles are given in the Introduction in the section GeoSPARQL Standard structure.
ii. Submitting organizations
The following organizations submitted this Implementation Standard to the Open Geospatial Consortium Inc.:
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CSIRO
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Cubewerx Inc.
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Defence Science and Technology Laboratory (DSTL)
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Geonovum
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Geoscape Australia
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Geoscience Australia
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Mainz University Of Applied Sciences
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Oracle America
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OSGeo
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SURROUND Australia Pty Ltd.
iii. Submission contact points
All questions regarding this submission should be directed to the editor or the submitters:
| Contact | Company |
|---|---|
Simon J.D. Cox |
CSIRO |
Panagiotis (Peter) A. Vretanos |
Cubewerx Inc. |
Paul Cripps |
DSTL |
Linda van den Brink |
Geonovum |
Joseph Abhayaratna |
Geoscape Australia |
Irina Bastrakova |
Geoscience Australia |
Timo Homburg |
Mainz University Of Applied Sciences |
Matthew Perry |
Oracle America |
Dimitris Kotzinos |
OSGeo |
Nicholas J. Car |
SURROUND Australia Pty Ltd. |
Clarifications
-
The terms Spatial Reference System (SRS) and Coordinate Reference System (CRS) are no longer interchangeable. Spatial Reference System is now taken to be a broader category than Coordinate Reference System. These are defined in the Clause 4 section.
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Class definitions were updated to be more self-contained and easier to understand for people without a background in geoinformatics. The definitions are no longer dependent on other standards' definitions, only informed by them.
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A section was added on the specification of units of measurement.
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A section was added on the [Influence of Coordinate Reference Systems on geometric computations].
v. Changes to the OGC® Abstract Specification
The OGC® Abstract Specification does not require changes to accommodate this OGC® standard.
Foreword
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. Open Geospatial Consortium shall not be held responsible for identifying any or all such patent rights. However, to date, no such rights have been claimed or identified.
Recipients of this document are requested to submit, with their comments, notification of any relevant patent claims or other intellectual property rights of which they may be aware that might be infringed by any implementation of the specification set forth in this document, and to provide supporting documentation.
Introduction
The W3C Semantic Web Activity defines a collection of technologies that enables a “web of data” where information is easily shared and reused across applications. Some key pieces of this technology stack are the Resource Description Framework (RDF) data model [RDF], [RDFS], the OWL Web Ontology Language [OWL2] and the SPARQL Protocol and RDF Query Language [SPARQL].
RDF
RDF is, among other things, a data model built on edge-node "graphs." Each link in a graph consists of three elements (with many aliases depending on the mapping from other types of data models):
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Subject (start node, instance, entity, feature)
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Predicate (verb, property, attribute, relation, member, link, reference)
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Object (value, end node, non-literal values can be used as a Subject)
Any of the three values in a triple can be represented with an Internationalized Resource Identifier (IRI) [IETF3987], which globally and uniquely identifies the resource referenced. IRIs are an extension to Uniform Resource Identifiers (URIs) that allow for non-ASCII characters. In addition to functioning as identifiers, IRIs are usually, but not necessarily, resolvable. This means a person or machine can "dereference" them (click on them or otherwise execute them) and be taken to more information about the resource, perhaps in a web browser.
Subjects and objects within an RDF triple are called nodes and can also be represented with a blank node (a local identifier without meaning outside the graph it is defined within). Objects can further be represented with a literal value. RDF uses the basic literal values from XML [XSD2] however the basic types can be extended for specialized purposes. Indeed, this document extends the basic types to include geometry data. The figure below shows a basic triple.
Note that the same node may be a subject in some triples, and an object in others.
Almost all data can be presented or represented in RDF. In particular, there are similarities to the (feature-instance-by-id, attribute, value) tuples of the General Feature Model [ISO19109], and to the relational model as well (table primary key, column, value).
SPARQL
From [SPARQL]:
SPARQL … is a set of specifications that provide languages and protocols to query and manipulate RDF graph content on the Web or in an RDF store.
From Wikipedia[1]:
SPARQL (pronounced "sparkle", a recursive acronym for SPARQL Protocol and RDF Query Language) is an RDF query language - that is, a semantic query language for databases — able to retrieve and manipulate data stored in Resource Description Framework (RDF) format. It was made a standard by the RDF Data Access Working Group (DAWG) of the World Wide Web Consortium, and is recognized as one of the key technologies of the semantic web. On 15 January 2008, SPARQL 1.0 was acknowledged by W3C as an official recommendation, and SPARQL 1.1 in March, 2013.
SPARQL queries work on RDF representations of data by finding patterns that match templates in the query, in effect finding information graphs in the RDF data based on the templates and filters (constraints on nodes and edges) expressed in the query. This query template is represented in the SPARQL query by a set of parameterized “query variables” appearing in a sequence of RDF triples and filters. If the query processor finds a set of triples in the data (converted to an RDF graph in some predetermined standard manner) then the values that the “query variables” take on in those triples become a solution to the query request. The values of the variables are returned in the query result in a format based on the “SELECT” clause of the query (similar to SQL).
In addition to predicates defined in this manner, the SPARQL query may contain filter functions that can be used to further constrain the query. Several mechanisms are available to extend filter functions to allow for predicates calculated directly on data values. Section 17.6[2] of the SPARQL specification [SPARQL] describes the mechanism for invocation of such a filter function.
The OGC GeoSPARQL Standard supports representing and querying geospatial data on the Semantic Web. GeoSPARQL defines a vocabulary for representing geospatial data in RDF. It also defines extensions to the SPARQL query language for processing geospatial data.
GeoSPARQL does not directly provide support for temporality. Predicates for temporal relations may be used from the OWL Time Ontology [TIME], but query extension functions for spatiotemporal operations are not present in the GeoSPARQL standard.
GeoSPARQL Standard structure
The GeoSPARQL Standard consists of multiple parts, or profile resources. The comprehensive listing of these parts is given in the GeoSPARQL profile definition, (see http://www.opengis.net/def/geosparql). Below is an overview of the major parts:
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profile definition
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Formally defined as an ontology, defined according to the Profiles Vocabulary [PROF];
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This relates the parts in the standard together, provides access to them, and declares dependencies on other standards.
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Standard document (this document)
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Defines many of the standard’s parts;
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Includes normative RDF/OWL [RDF],[OWL2] ontology element definitions, conformance requirements and function signatures based on the General Feature Model [ISO19109], Simple Features [OGCSFACA] [ISO19125-1] and SQL MM [ISO13249];
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Also includes non-normative examples and mappings to other modelling and function systems.
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Domain model RDF/OWL [RDF],[OWL2] ontology
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For geographic information representation;
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Based on the General Feature Model [ISO19109], Simple Features Access [OGCSFACA] [ISO19125-1], Geography Markup Language [GML] and SQL MM [ISO13249]
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Defined within the specification document and also delivered in RDF.
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Functions & Rules vocabulary
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Derived from the ontology;
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Presented as a [SKOS] taxonomy.
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Simple Features vocabulary
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Derived from the class model defined in Simple Features Access [OGCSFACA] [ISO19125-1];
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Presented as an OWL Section 4.1.3 ontology.
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SPARQL [SPARQL] extension functions defined within this document.
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RDF data validator
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Defined using SHACL [SHACL];
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Presented within a single RDF file.
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SPARQL 1.1 Service description for GeoSPARQL
This document follows a modular design and contains the following components:
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A core component defining the top-level RDFS/OWL classes for spatial objects.
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A topology vocabulary component defining the RDF properties for asserting and querying topological relationships between spatial objects.
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A geometry component defining RDFS data types for serializing geometry data, geometry-related RDF properties, and non-topological spatial query functions for geometry objects.
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A geometry topology component defining topological query functions.
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An RDFS entailment component defining mechanisms for matching implicit RDF triples that are derived based on RDF and RDFS semantics.
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A query rewrite component defining rules for transforming a simple triple pattern that tests a topological relationship between two features into an equivalent query involving concrete geometries and topological query functions.
Each of these components forms a set of Requirements known as a GeoSPARQL Conformance Class. Implementations can provide various levels of functionality by choosing which Conformance Classes to support. For example, a system based purely on qualitative spatial reasoning may support only the core and topological vocabulary Classes.
In addition, GeoSPARQL is designed to accommodate systems based on qualitative spatial reasoning and systems based on quantitative spatial computations. Systems based on qualitative spatial reasoning, (e.g. those based on Region Connection Calculus [QUAL], [LOGIC]) do not usually model explicit geometries, so queries in such systems will likely test for binary spatial relationships between features rather than between explicit geometries. To allow queries for spatial relationships between features in quantitative systems, GeoSPARQL defines a series of query transformation rules that expand a feature-only query into a geometry-based query. With these transformation rules, queries about spatial relationships between features will have the same specification in both qualitative systems and quantitative systems. The qualitative system will likely evaluate the query with a backward-chaining spatial “reasoner”, and the quantitative system can transform the query into a geometry-based query that can be evaluated with computational geometry.
OGC GeoSPARQL - A Geographic Query Language for RDF Data
1. Scope
The OGC GeoSPARQL Standard is comprised of multiple parts. See the Introduction section GeoSPARQL Standard structure for details of the parts.
GeoSPARQL does not define a comprehensive vocabulary for representing spatial information. Instead GeoSPARQL defines a core set of classes, properties and datatypes that can be used to construct query patterns. Many useful extensions to this vocabulary are possible, and we intend for the Semantic Web and Geospatial communities to develop additional vocabularies for describing spatial information.
2. Conformance
Conformance with this Standard shall be checked using all the relevant tests specified in Annex A - Abstract Test Suite (normative). The framework, concepts, and methodology for testing, and the criteria to be achieved to claim conformance are specified in ISO 19105: Geographic information — Conformance and Testing [ISO19105].
This document establishes many individual Requirements and Conformance Classes which contain tests for one or more Requirements. GeoSPARQL implementations need not conform to all Conformance Classes but must state which individual ones they do conform to. GeoSPARQL implementations claiming conformance to a Conformance Class must pass all the tests defined for it in Annex A - Abstract Test Suite (normative).
Requirements and Conformance Class tests have IRIs that are relative to versioned namespace IRIs. Requirements and Conformance Class tests that are defined in GeoSPARQL 1.0 have IRIs relative to http://www.opengis.net/spec/geosparql/1.0/ and those added in GeoSPARQL 1.1 have IRIs relative to http://www.opengis.net/spec/geosparql/1.1/.
Many Conformance Classes are parameterized, and any parameters are explained in the detailed clauses for those Conformance Classes.
| Conformance Class | Description | Subclause of the abstract test suite |
|---|---|---|
Core |
Defines top-level spatial vocabulary components |
A.1 |
Topology Vocabulary Extension |
Defines topological relation vocabulary |
A.2 |
Geometry Extension |
Defines geometry vocabulary and non-topological query functions |
A.3 |
Geometry Extension - DGGS |
Defines the properties and functions of the Geometry Extension Conformance Classes for use with Discrete Global Grid System geometry representations |
A.3.DGGS |
Geometry Topology Extension |
Defines topological query functions for geometry objects |
A.4 |
RDFS Entailment Extension |
Defines a mechanism for matching implicit RDF triples that are derived based on RDF and RDFS semantics |
A.5 |
Query Rewrite Extension |
Defines query transformation rules for computing spatial relations between spatial objects based on their associated geometries |
A.6 |
Dependencies between each GeoSPARQL Conformance Class are shown below in Figure 2. To support a Conformance Class for a given set of parameter values, an implementation must support each dependent Conformance Class with the same set of parameter values.
3. Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, subsequent amendments to, or revisions of, any of these publications do not apply. However, parties to agreements based on this document are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest edition of the normative document referred to applies.
Items in this list are linked to their full citation in the Bibliography.
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[OGCSFACA] [ISO19125-1], ISO 19125-1: Geographic information — Simple feature access — Part 1: Common architecture
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[OGCOM] [ISO19156], ISO 19156: Geographic information — Observations and measurements
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[OGC07-036], OGC 07-036: Geography Markup Language (GML) Encoding Standard
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[IETF3987], Internet Engineering Task Force, RFC 3987: Internationalized Resource Identifiers (IRIs)
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[OWL2] OWL 2 Web Ontology Language Document Overview (Second Edition)
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[RDF], RDF 1.1 Concepts and Abstract Syntax
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[RDFS] RDF Schema 1.1
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[RIFCORE], RIF Core Dialect (Second Edition)
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[SPARQL], SPARQL 1.1 Query Language
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[SPARQLENT], SPARQL 1.1 Entailment Regimes
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[SPARQLPROT], SPARQL 1.1 Protocol
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[SPARQLRESX], SPARQL Query Results XML Format (Second Edition)
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[SPARQLRESJ], SPARQL 1.1 Query Results JSON Format
4. Terms and definitions
For the purposes of this document, the terms and definitions given in the above normative references apply, as well as those reproduced or created in this section.
4.1. Semantic Web
The following terms and their definitions relate to Semantic Web models, tools and methods.
4.1.1. RDF
The Resource Description Framework (RDF) is a framework for representing information in the Web. RDF graphs are sets of subject-predicate-object triples, where the elements may be IRIs, blank nodes, or datatyped literals. They are used to express descriptions of resources. [RDF]
4.1.2. RDFS
RDF Schema provides a data-modelling vocabulary for RDF data. RDF Schema is an extension of the basic RDF vocabulary. [RDFS]
4.1.3. OWL
The OWL 2 Web Ontology Language, informally OWL 2, is an ontology language for the Semantic Web with formally defined meaning. OWL 2 ontologies provide classes, properties, individuals, and data values and are stored as Semantic Web documents. OWL 2 ontologies can be used along with information written in RDF, and OWL 2 ontologies themselves are primarily exchanged as RDF documents. [OWL2]
4.1.4. SPARQL
SPARQL is a query language for RDF. The results of SPARQL queries can be result sets or RDF graphs. [SPARQL]
4.2. Spatial
The following terms and their definitions relate to spatial science and data.
4.2.1. coordinate system
A coordinate system is a set of mathematical rules for specifying how coordinates are to be assigned to points.
4.2.2. coordinate reference system
A coordinate reference system (CRS) is a coordinate system that is related to an object by a datum.
4.2.3. datum
A datum is a parameter or set of parameters that define the position of the origin, the scale, and the orientation of a coordinate system.
4.2.4. discrete global grid system
A discrete global grid system (DGGS) is a spatial reference system that represents the Earth, or any other globe-like object, with a tessellation of nested cells. Generally, a DGGS will exhaustively partition the globe in closely packed hierarchical tessellations, each cell representing a homogenous value, with a unique identifier or indexing that allows for linear ordering, parent-child operations, and nearest neighbor algebraic operations.
4.2.5. spatial reference system
A spatial reference system (SRS) is a system for establishing spatial position. A spatial reference system can use geographic identifiers (place names, for example), coordinates (in which case it is a coordinate reference system), or identifiers with structured geometry (in which case it is a discrete global grid system).
5. Conventions
5.1. Symbols and abbreviated terms
In this specification, the following common acronyms are used:
CRS |
Coordinate Reference System |
DGGS |
Discrete Global Grid System |
GeoJSON |
Geographic JavaScript Object Notation |
GFM |
General Feature Model (as defined in ISO 19109) |
GIS |
Geographic Information System |
GML |
Geography Markup Language |
IRI |
Internationalized Resource Identifier |
KML |
Keyhole Markup Language |
OWL |
OWL 2 Web Ontology Language |
RCC |
Region Connection Calculus |
RDF |
Resource Description Framework |
RDFS |
RDF Schema |
RIF |
Rule Interchange Format |
SPARQL |
SPARQL Protocol and RDF Query Language |
SQL |
Structured Query Language |
SRS |
Spatial Reference System |
URI |
Universal Resource Identifier |
WKT |
Well Known Text (as defined by Simple Features or ISO 19125) |
W3C |
World Wide Web Consortium (http://www.w3.org/) |
XML |
Extensible Markup Language |
5.2. Namespaces
The following IRI namespace prefixes are used throughout this document:
ex: |
|
geo: |
|
geof: |
|
geor: |
|
gml: |
|
my: |
|
ogc: |
|
owl: |
|
rdf: |
|
rdfs: |
|
sf: |
|
skos: |
|
xsd: |
5.3. Placeholder IRIs
All of these namespace prefixes in the previous section resolve to resources that contain their namespace content except for ex: (http://example.com/), which is used just for examples, and ogc: (http://www.opengis.net/), which is used as a placeholder, for example, ogc:geomLiteral is used to indicate any one of the specific geometry literal serializations defined here, such as geo:wktLiteral.
6. Core
This clause establishes the Core Requirements class, with IRI /req/core, which has a corresponding Conformance Class, Core, with IRI /conf/core. These Requirements define a set of classes and properties for representing geospatial data. The resulting vocabulary - an ontology - can be used to construct SPARQL graph patterns for querying appropriately modeled geospatial data. The RDFS and OWL vocabularies have both been used so that the vocabulary can be understood by systems that support only RDFS entailment and by systems that support OWL-based reasoning.
The figure below gives an overview of the classes and properties defined by GeoSPARQL in the Core, Topology Vocabulary Extension and Geometry Extension, Geometry Topology Extension and RDFS Entailment Extension Conformance Classes.
geo:hasSize, its metric equivalent and geo:hasSerialization are not shown for clarity.6.1. SPARQL
Req 1 Implementations shall support the SPARQL Query Language for RDF [SPARQL], the SPARQL Protocol [SPARQLPROT] and the SPARQL Query Results XML [SPARQLRESX] and JSON [SPARQLRESJ] Formats. |
|
6.2. Classes
Two main classes are defined: geo:SpatialObject and geo:Feature.
Two container classes are defined: Spatial Object Collection and Feature Collection.
6.2.1. Class: geo:SpatialObject
The class geo:SpatialObject is defined by the following:
geo:SpatialObject
a rdfs:Class, owl:Class ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "Spatial Object"@en ;
skos:definition "Anything spatial (being or having a shape, position or an extent)."@en ;
skos:note "Subclasses of this class are expected to be used for instance data."@en ;
.Req 2 Implementations shall allow the RDFS class |
|
Example:
eg:x
a geo:SpatialObject ;
skos:prefLabel "Object X";
.6.2.2. Class: geo:Feature
The class geo:Feature is equivalent to the class GFI_Feature [OGCOM] [ISO19156] and is defined by the following:
geo:Feature
a rdfs:Class, owl:Class ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "Feature"@en ;
rdfs:subClassOf geo:SpatialObject ;
owl:disjointWith geo:Geometry ;
skos:definition "A discrete spatial phenomenon in a universe of discourse."@en ;
skos:note "A Feature represents a uniquely identifiable phenomenon, for example
a river or an apple. While such phenomena (and therefore the Features
used to represent them) are bounded, their boundaries may be crisp
(e.g., the declared boundaries of a state), vague (e.g., the
delineation of a valley versus its neighboring mountains), and change
with time (e.g., a storm front). While discrete in nature, Features
may be created from continuous observations, such as an isochrone
that determines the region that can be reached by ambulance within
5 minutes."@en ;
.Req 3 Implementations shall allow the RDFS class |
|
6.2.3. Class: geo:SpatialObjectCollection
The class geo:SpatialObjectCollection is defined by the following:
geo:SpatialObjectCollection
a owl:Class ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "Spatial Object Collection" ;
skos:definition "A collection of individual Spatial Objects."@en ;
skos:note "This is the superclass of Feature Collection and Geometry Collection."@en ;
rdfs:subClassOf rdfs:Container ;
rdfs:subClassOf [
a owl:Restriction ;
owl:allValuesFrom geo:SpatialObject ;
owl:onProperty rdfs:member ;
] ;
.Membership of the generic rdfs:Container that defines this class is restricted to instances of Spatial Object. Spatial Object Collection members are to be indicated with the rdfs:member property.
Req 4 Implementations shall allow the RDFS class |
|
6.2.4. Class: geo:FeatureCollection
The class geo:FeatureCollection is defined by the following:
geo:FeatureCollection
a owl:Class ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "Feature Collection" ;
skos:definition "A collection of individual Features."@en ;
rdfs:subClassOf geo:SpatialObjectCollection ;
rdfs:subClassOf [
a owl:Restriction ;
owl:allValuesFrom :Feature ;
owl:onProperty rdfs:member ;
] ;
.Membership of the more general Spatial Object Collection that defines this class is restricted to instances of Feature. geo:FeatureCollection members are to be indicated with the rdfs:member property.
Req 5 Implementations shall allow the RDFS class |
|
6.3. Standard Properties for geo:SpatialObject
Properties are defined for associating Spatial Objects with scalar spatial measurements (sizes) .
Req 6 Implementations shall allow the properties
|
|
6.3.1. Property: geo:hasSize
The property geo:hasSize is the superproperty of all properties that can be used to indicate the size of a Spatial Object in case (only) metric units (meter, square meter or cubic meter) cannot be used. If it is possible to express size in metric units, subproperties of geo:hasMetricSize should be used.
This property has no range specification. This makes it possible to use other vocabularies for expressions of size, for example vocabularies for units of measurement or vocabularies for specifying measurement quality.
GeoSPARQL 1.1 defines the following subproperties of this property:
geo:hasLength,
geo:hasPerimeterLength,
geo:hasArea and
geo:hasVolume.
geo:hasSize
a rdf:Property, owl:ObjectProperty ;
rdfs:isDefinedBy geo: ;
rdfs:domain geo:SpatialObject ;
skos:definition "Subproperties of this property are used to indicate the size of a
Spatial Object as a measurement or estimate of one or more dimensions
of the Spatial Object's spatial presence."@en ;
skos:prefLabel "has size"@en ;
.6.3.2. Property: geo:hasMetricSize
The property geo:hasMetricSize is the superproperty of all properties that can be used to indicate the size of a Spatial Object using metric units (meter, square meter or cubic meter). Using a subproperty of this property is the recommended way to specify size, because using a standard unit of length (meter) benefits data interoperability and simplicity. Subproperties of geo:hasSize can be used if more complex expressions are necessary, for example if the unit of length cannot be converted to meter, or if additional data are needed to describe the measurement or estimate of size.
GeoSPARQL 1.1 defines the following subproperties of this property:
geo:hasMetricLength,
geo:hasMetricPerimeterLength,
geo:hasMetricArea and
geo:hasMetricVolume.
geo:hasMetricSize
a rdf:Property, owl:DatatypeProperty ;
rdfs:isDefinedBy geo: ;
rdfs:domain geo:SpatialObject ;
rdfs:range xsd:double ;
skos:definition "Subproperties of this property are used to indicate the size of a
Spatial Object, as a measurement or estimate of one or more dimensions
of the Spatial Object's spatial presence. Units are always metric
(meter, square meter or cubic meter)."@en ;
skos:prefLabel "has metric size"@en ;
.6.3.3. Property: geo:hasLength
The property geo:hasLength can be used to indicate the length of a Spatial Object if it is not possible to use the property geo:hasMetricLength. It is a subproperty of geo:hasSize.
geo:hasLength
a rdf:Property, owl:ObjectProperty ;
rdfs:isDefinedBy geo: ;
rdfs:subPropertyOf geo:hasSize ;
rdfs:domain geo:SpatialObject ;
skos:definition "The length of a Spatial Object."@en ;
skos:prefLabel "has length"@en ;
.6.3.4. Property: geo:hasMetricLength
The property geo:hasMetricLength can be used to indicate the length of a Spatial Object in meters (m). It is a subproperty of geo:hasMetricSize. This property can be used for Spatial Objects having one, two, or three dimensions.
geo:hasMetricLength
a rdf:Property, owl:DatatypeProperty ;
rdfs:isDefinedBy geo: ;
rdfs:subPropertyOf geo:hasMetricSize ;
rdfs:domain geo:SpatialObject ;
rdfs:range xsd:double ;
skos:definition "The length of a Spatial Object in meters."@en ;
skos:prefLabel "has length in meters"@en ;
.6.3.5. Property: geo:hasPerimeterLength
The property geo:hasPerimeterLength can be used to indicate the length of the outer boundary of a Spatial Object if it is not possible to use the property geo:hasMetricPerimeterLength. It is a subproperty of geo:hasSize.
geo:hasPerimeterLength
a rdf:Property, owl:ObjectProperty ;
rdfs:isDefinedBy geo: ;
rdfs:subPropertyOf geo:hasSize ;
skos:definition "The length of the perimeter of a Spatial Object."@en ;
skos:prefLabel "has perimeter length"@en ;
.6.3.6. Property: geo:hasMetricPerimeterLength
The property geo:hasMetricPerimeterLength can be used to indicate the length of the outer boundary of a Spatial Object in meters (m). It is a subproperty of geo:hasMetricSize. Circumference is considered a type of perimeter, so this property can be used for circular or curved objects too. This property can be used for Spatial Objects having two or three dimensions.
geo:hasMetricPerimeterLength
a rdf:Property, owl:DatatypeProperty ;
rdfs:isDefinedBy geo: ;
rdfs:subPropertyOf geo:hasMetricSize ;
rdfs:domain geo:SpatialObject ;
rdfs:range xsd:double ;
skos:definition "The length of the perimeter of a Spatial Object in meters."@en ;
skos:prefLabel "has perimeter length in meters"@en ;
.|
Tip
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A consistency check can be applied to Geometry instances indicating both this property and the property geo:dimension: if supplied, the geo:dimension property’s range value must be the literal integer 2 or 3. The following SPARQL query will return true if applied to a graph where this is not the case for all Geometries:
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PREFIX geo: <http://www.opengis.net/ont/geosparql#>
ASK
WHERE {
?g geo:hasMetricPerimeterLength ?p ;
geo:dimension ?d .
FILTER (?d < 2)
}6.3.7. Property: geo:hasArea
The property geo:hasArea can be used to indicate the area of a Spatial Object if it is not possible to use the property geo:hasMetricArea. It is a subproperty of geo:hasSize.
geo:hasArea
a rdf:Property, owl:ObjectProperty ;
rdfs:isDefinedBy geo: ;
rdfs:subPropertyOf geo:hasSize ;
rdfs:domain geo:SpatialObject ;
skos:definition "The area of a Spatial Object."@en ;
skos:prefLabel "has area"@en ;
.6.3.8. Property: geo:hasMetricArea
The property geo:hasMetricArea can be used to indicate the area of a Spatial Object in square meters (m2). It is a subproperty of geo:hasMetricSize. This property can be used for Spatial Objects having two or three dimensions.
geo:hasMetricArea
a rdf:Property, owl:DatatypeProperty ;
rdfs:isDefinedBy geo: ;
rdfs:subPropertyOf geo:hasMetricSize ;
rdfs:domain geo:SpatialObject ;
rdfs:range xsd:double ;
skos:definition "The area of a Spatial Object in square meters."@en ;
skos:prefLabel "has area in meters"@en ;
.|
Tip
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A consistency check can be applied to Geometry instances indicating both this property and the property geo:dimension: if supplied, the geo:dimension property’s range value must be the literal integer 2 or 3. The following SPARQL query will return true if applied to a graph where this is not the case for all Geometries:
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PREFIX geo: <http://www.opengis.net/ont/geosparql#>
ASK
WHERE {
?g geo:hasMetricArea ?a ;
geo:dimension ?d .
FILTER (?d < 2)
}6.3.9. Property: geo:hasVolume
The property geo:hasVolume can be used to indicate the volume of a Spatial Object if it is not possible to use the property geo:hasMetricVolume. It is a subproperty of geo:hasSize.
geo:hasVolume
a rdf:Property, owl:ObjectProperty ;
rdfs:isDefinedBy geo: ;
rdfs:subPropertyOf geo:hasSize ;
rdfs:domain geo:SpatialObject ;
skos:definition "The volume of a three-dimensional Spatial Object."@en ;
skos:prefLabel "has volume"@en ;
.6.3.10. Property: geo:hasMetricVolume
The property geo:hasMetricVolume can be used to indicate the volume of a Spatial Object in cubic meters (m3). It is a subproperty of geo:hasMetricSize. This property can be used for Spatial Objects having three dimensions.
geo:hasMetricVolume
a rdf:Property, owl:DatatypeProperty ;
rdfs:isDefinedBy geo: ;
rdfs:subPropertyOf :hasMetricSize ;
rdfs:domain geo:SpatialObject ;
rdfs:range xsd:double ;
skos:definition "The volume of a Spatial Object in cubic meters."@en ;
skos:prefLabel "has area in meters"@en ;
.|
Tip
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A consistency check can be applied to Geometries indicating both this property and the property geo:dimension: if supplied, the property geo:dimension property’s range value must be the literal integer 3. The following SPARQL query will return true if applied to a graph where this is not the case for all Geometries:
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PREFIX geo: <http://www.opengis.net/ont/geosparql#>
ASK
WHERE {
?g geo:hasMetricVolume ?v ;
geo:dimension ?d .
FILTER (?d != 3)
}6.4. Standard Properties for geo:Feature
Properties are defined for associating geo:Feature instances with geo:Geometry instances.
Req 7 Implementations shall allow the properties
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6.4.1. Property: geo:hasGeometry
The property geo:hasGeometry is used to link a Feature with a Geometry that represents its spatial extent. A given Feature may have many associated geometries.
geo:hasGeometry
a rdf:Property, owl:ObjectProperty ;
rdfs:isDefinedBy geo: ;
rdfs:domain geo:Feature ;
rdfs:range geo:Geometry ;
skos:prefLabel "has Geometry"@en ;
skos:definition "A spatial representation for a given Feature."@en ;
.6.4.2. Property: geo:hasDefaultGeometry
The property geo:hasDefaultGeometry is used to link a Feature with its default Geometry. The default geometry is the Geometry that should be used for spatial calculations in the absence of a request for a specific geometry (e.g. in the case of query rewrite).
geo:hasDefaultGeometry
a rdf:Property, owl:ObjectProperty ;
rdfs:isDefinedBy geo: ;
rdfs:domain geo:Feature ;
rdfs:range geo:Geometry ;
skos:prefLabel "has Default Geometry"@en ;
skos:definition "The default geometry to be used in spatial calculations,
usually the most detailed geometry."@en ;
rdfs:subPropertyOf geo:hasGeometry ;
.GeoSPARQL does not restrict the cardinality of the has default geometry property. It is thus possible for a Feature to have more than one distinct default geometry or to have no default geometry. This situation does not result in a query processing error; SPARQL graph pattern matching simply proceeds as normal. Certain queries may, however, give logically inconsistent results. For example, if a Feature my:f1 has two asserted default geometries, and those two geometries are disjoint polygons, the query below could return a non-zero count on a system supporting the GeoSPARQL Query Rewrite Extension (rule geor:sfDisjoint).
PREFIX geo: <http://www.opengis.net/ont/geosparql#>
SELECT (COUNT(*) AS ?cnt)
WHERE { :f1 geo:sfDisjoint :f1 }Such cases are application-specific data modeling errors and are therefore outside of the scope of the GeoSPARQL specification, however it is recommended that multiple geometries indicated with geo:hasDefaultGeometry should be differentiated by Geometry class properties, perhaps relating to precision, SRS etc.
6.4.3. Property: geo:hasBoundingBox
The property geo:hasBoundingBox is used to link a Feature with a simplified geometry-representation corresponding to the envelope of the feature’s geometry. Bounding-boxes are typically used in indexing and discovery.
geo:hasBoundingBox
a rdf:Property, owl:ObjectProperty ;
rdfs:isDefinedBy geo: ;
rdfs:subPropertyOf geo:hasGeometry ;
rdfs:domain geo:Feature ;
rdfs:range geo:Geometry ;
skos:prefLabel "has bounding box"@en ;
skos:definition "The minimum or smallest bounding or enclosing box of a given Feature."@en ;
skos:scopeNote "The target is a geometry that defines a rectilinear region whose edges are
aligned with the axes of the coordinate reference system, which exactly
contains the geometry or Feature e.g. sf:Envelope"@en ;
.GeoSPARQL does not restrict the cardinality of the geo:hasBoundingBox property. A Feature may be associated with more than one bounding-box, for example in different coordinate reference systems.
6.4.4. Property: geo:hasCentroid
The property geo:hasCentroid is used to link a Feature with a point geometry corresponding with the centroid of its geometry. The centroid is typically used to show location on a low-resolution image, and for some indexing and discovery functions.
geo:hasCentroid
a rdf:Property, owl:ObjectProperty ;
rdfs:isDefinedBy geo: ;
rdfs:subPropertyOf geo:hasGeometry ;
rdfs:domain geo:Feature ;
rdfs:range geo:Geometry ;
skos:prefLabel "has centroid"@en ;
skos:definition "The arithmetic mean position of all the geometry points
of a given Feature."@en ;
skos:scopeNote "The target geometry shall describe a point, e.g. sf:Point"@en ;
.GeoSPARQL does not restrict the cardinality of the geo:hasCentroid property. A Feature may be associated with more than one centroid, for example computed using different rules or in different coordinate reference systems.
7. Topology Vocabulary Extension
This clause establishes the Topology Vocabulary Extension parameterized Requirements class. The IRI base is /req/topology-vocab-extension, which has a single corresponding Conformance Class Topology Vocabulary Extension, with IRI /conf/topology-vocab-extension. This Requirements class defines a vocabulary for asserting and querying topological relations between spatial objects. The class is parameterized so that different families of topological relations may be used, such as RCC8 and Egenhofer. These relations are generalized so that they may connect features as well as geometries.
A Dimensionally Extended 9-Intersection Model [DE-9IM] pattern, which specifies the spatial dimension of the intersections of the interiors, boundaries and exteriors of two geometric objects, is used to describe each spatial relation. Possible pattern values are -1 (empty), 0, 1, 2, T (true) = {0, 1, 2}, F (false) = {-1}, * (don’t care) = {-1, 0, 1, 2}. In the following descriptions, the notation X/Y is used to denote applying a spatial relation to geometry types X and Y (i.e., x relation y where x is of type X and y is of type Y). The symbol P is used for 0-dimensional geometries (e.g. points). The symbol L is used for 1-dimensional geometries (e.g. lines), and the symbol A is used for 2-dimensional geometries (e.g. polygons). Consult the Simple Features specification [OGCSFACA] [ISO19125-1] for a more detailed description of DE-9IM intersection patterns.
7.1. Parameters
The following parameter is defined for the Topology Vocabulary Extension Requirements.
relation_family: Specifies the set of topological spatial relations to support.
7.2. Simple Features Relation Family
This clause defines Requirements for the Simple Features relation family.
Req 8 Implementations shall allow the properties
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Topological relations in the Simple Features family are summarized in Table 2. Multi-row intersection patterns should be interpreted as a logical OR of each row.
| Relation Name | Relation IRI | Domain/Range | Applies To Geometry Types | DE-9IM Intersection Pattern |
|---|---|---|---|---|
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7.3. Egenhofer Relation Family
This clause defines Requirements for the 9-intersection model for the binary topological relations (Egenhofer) relation family. The reader should consult references [FORMAL] and [CATEG] for a more detailed discussion of Egenhofer relations.
Req 9 Implementations shall allow the properties
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Topological relations in the Egenhofer family are summarized in Table 3. Multi-row intersection patterns should be interpreted as a logical OR of each row.
| Relation Name | Relation IRI | Domain/Range | Applies To Geometry Types | DE-9IM Intersection Pattern |
|---|---|---|---|---|
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7.4. RCC8 Relation Family
This clause defines Requirements for the region connection calculus basic 8 (RCC8) relation family. The reader should consult references [QUAL] and [LOGIC] for a more detailed discussion of RCC8 relations.
Req 10 Implementations shall allow the properties
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Topological relations in the RCC8 family are summarized in Table 4.
| Relation Name | Relation IRI | Domain/Range | Applies To Geometry Types | DE-9IM Intersection Pattern |
|---|---|---|---|---|
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7.5. Equivalent RCC8, Egenhofer and Simple Features Topological Relations
Table 5 summarizes the equivalences between Egenhofer, RCC8 and Simple Features spatial relations for closed, non-empty regions. The symbol + denotes logical OR, and the symbol ¬ denotes negation.
| Simple Features | RCC8 | Egenhofer |
|---|---|---|
equals |
equals |
equals |
disjoint |
disconnected |
disjoint |
intersects |
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touches |
externally connected |
meet |
within |
non-tangential proper part |
inside |
contains |
non-tangential proper part inverse |
contains |
overlaps |
partially overlapping |
overlap |
8. Geometry Extension
This clause defines the Geometry Extension parameterized Requirements class with the base IRI /req/geometry-extension. There is a single corresponding conformance class Geometry Extension, with the IRI /conf/geometry-extension. These Requirements define a vocabulary for asserting and querying information about geometry data, and define query functions for operating on geometry data.
As part of the vocabulary, RDFS datatypes are defined for encoding detailed geometry information as a literal value. A literal representation of a geometry is needed so that geometric values may be treated as a single unit. Such a representation allows geometries to be passed to external functions for computations and to be returned from a query.
8.1. Rationale
Other schemes for encoding simple geometry data in RDF have been implemented. The W3C Basic Geo vocabulary[3] was an early (2003) RDF vocabulary for "representing lat(itude), long(itude) and other information about spatially-located things. Geo specifies WGS84 as the reference datum". Further, many widely used Semantic Web vocabularies contain some spatial data support. For example, Dublin Core Terms provides a Location class[4] for "A spatial region or named place." and schema.org provides a number of spatial object and geometry classes, such as GeoCoordinates [5] and GeoShape [6].
Many vocabularies such as the above provide little specific support for detailed geometries and only specify using the WGS84 Coordinate Reference System (CRS).
Since the first version of GeoSPARQL, many ontologies have imported GeoSPARQL. For example, the ISA Programme Location Core Vocabulary [7] whose usage notes provide examples containing GeoSPARQL literals and the use of GeoSPARQL’s "geometry class". The W3C’s more recent Data Catalog Vocabulary, Version 2 (DCAT2) standard[8] similarly contains usage notes for geometry, bbox and other properties that suggest the use of GeoSPARQL literals.
Some of the properties defined in these vocabularies, such as DCAT2’s dcat:spatialResolution have motivated the inclusion of new properties in this version of GeoSPARQL. In this case the equivalent property is geo:hasSpatialResolution. The GeoSPARQL 1.1 Standards Working Group charter [CHARTER] contains references to a number of vocabularies/ontologies that were influential in the generation of this version of GeoSPARQL.
8.2. GeoSPARQL and Simple Features (SFA-CA)
The GeoSPARQL Geometry Extension is largely based on the ISO/OGC Simple Features Access - Common Architecture (SFA-CA) Standard [OGCSFACA]. Contrary to what the name may imply, SFA-CA is about Geometry and not about Features. SFA-CA describes simple geometry, meaning that geometric shapes are based on points and straight lines (linear interpolations) between points. Within a single Geometry, these lines may not cross.
Neither GeoSPARQL nor SFA-CA support full three dimensional geometry. Coordinates may be three-dimensional, which means that points may have a Z-coordinate next to an X- and Y-coordinate. The Z-coordinate then holds the value of height or depth. However, lines or surfaces can only have one Z value for any explicit or interpolated X,Y pair. This approach is often referred to as 2.5 dimensional geometry. Geometric functions working with Geometries that have Z values will ignore Z values in calculations and first project geometry onto the Z=0 level.
SFA-CA also describes M coordinate values that may be part of geometry encodings. The M value represents a measure, a value that can be used in information systems that support linear referencing. GeoSPARQL at the moment does not support linear referencing. Like Z values in coordinates, M values are to be ignored.
SFA-CA specifies a class hierarchy for Geometry. Although these classes are not part of the GeoSPARQL ontology, the GeoSPARQL SWG does publish a vocabulary of Simple Features geometry: http://www.opengis.net/ont/sf. Geometry types defined in this vocabulary can be considered safe to use with GeoSPARQL. The two Geometry serializations that were specified in GeoSPARQL 1.0, WKT and GML, fully support all SFA-CA geometry types. However, the two Geometry serializations that were introduced in GeoSPARQL 1.1 do not. Some SFA-CA geometry types are not supported by either the OGC KML [OGCKML] or the GeoJSON format. For example, neither KML nor GeoJSON support the Triangulated Integrated Network (TIN) or Triangle geometry types.
8.3. Recommendation for units of measure
For geometric data to be interpreted and used correctly, the units of measure should be known. Typically, the particular Spatial Reference System (SRS) that is associated with a Geometry instance will specify a unit of measurement. However, some elements of GeoSPARQL allow arbitrary units of distance to be used, for example the property geo:hasSpatialResolution or the function geof:buffer. In those cases it is advisable to make use of a well-known web vocabulary for units of measurement. Making the unit of measurement explicit will improve data interoperability. The recommended vocabulary for units of measurement for GeoSPARQL is the Quantities, Units, Dimensions and Types (QUDT) ontology[9] but others may be used, as long as they are well-described.
8.4. Influence of Reference Systems on computations
A Geometry object consists of a set of coordinates and a specification on how the coordinates should be interpreted. This specification is known as a Spatial reference System (SRS). Taken together, coordinates and SRS allow performing computations on Geometry objects. For example, sizes can be calculated or new Geometry objects can be created. Some Spatial Reference Systems describe a two-dimensional flat space. In that case, coordinates are understood to be Cartesian, and Cartesian geometric computations can be performed. But Spatial Reference Systems can describe other types of spaces, to which Cartesian computations are not applicable. For example, if CRS <http://www.opengis.net/def/crs/OGC/1.3/CRS84> is used, coordinates are to be interpreted as decimal degrees of latitude and longitude, designating positions on a spheroid. The distance between two points using this CRS is different from the distance between two points that have the same coordinates but are based on a Cartesian CRS or other SRS.
To avoid erroneous computations involving Geometry, data publishers are recommended to clearly indicate the type of space that is described by the SRS.
8.5. Parameters
The following parameters are defined for the Geometry Extension Requirements.
- serialization
-
Specifies the serialization standard to use when generating geometry literals as well as the supported geometry types.
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Note
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A serialization strongly affects the geometry conceptualization. The WKT serialization aligns the geometry types with ISO 19125 Simple Features [OGCSFACA] [ISO19125-1]; the GML serialization aligns the geometry types with ISO 19107 Spatial Schema [ISO19107]. |
- version
-
Specifies the version of the serialization format used.
8.6. Geometry Class
A single root geometry class is defined: geo:Geometry. In addition, properties are defined for describing geometry data and for associating geometries with features.
One container class is defined: Geometry Collection.
8.6.1. Class: geo:Geometry
The class geo:Geometry is conceptually derived from UML class Geometry in [ISO19107] which is that standard’s "root class of the geometric object taxonomy and supports interfaces common to all geographically referenced geometric objects". geo:Geometry is defined by the following:
geo:Geometry
a rdfs:Class, owl:Class ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "Geometry"@en ;
rdfs:subClassOf geo:SpatialObject ;
owl:disjointWith geo:Feature;
skos:definition "A coherent set of direct positions in space. The positions
are held within a Spatial Reference System (SRS)."@en ;
skos:note "Geometry can be used as a representation of the shape, extent or
location of a Feature and may exist as a self-contained entity."@en ;
.Req 11 Implementations shall allow the RDFS class |
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8.6.2. Class: geo:GeometryCollection
The class Geometry Collection is defined by the following:
geo:GeometryCollection
a owl:Class ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "Geometry Collection"@en ;
skos:definition "A collection of individual Geometries."@en ;
rdfs:subClassOf geo:SpatialObjectCollection ;
rdfs:subClassOf [
a owl:Restriction ;
owl:allValuesFrom geo:Geometry ;
owl:onProperty rdfs:member ;
] ;
.Membership of the general Spatial Object Collection that defines this class is restricted to instances of Geometry. geo:GeometryCollection members are to be indicated with the rdfs:member property.
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Note
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There is no RDF/ontology relationship between this
Many geometry literal formats also have the ability to represent multiple geometries. Both the OGC Geography Markup Language (GML) and KML use a MultiGeometry type and Well Known Text (WKT) and GeoJSON use a GeometryCollection type. While the names of some of these objects are the same as this class' and all the concepts are similar, there is also no RDF/ontology relationship between this class and these literals. This class contains whole As per the expected use of |
Req 12 Implementations shall allow the RDFS class |
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8.7. Standard Properties for geo:Geometry
Properties are defined for describing geometry metadata.
Req 13 Implementations shall allow the properties
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8.7.1. Property: geo:dimension
The property geo:dimension is used to link a Geometry object to its topological dimension, which must be less than or equal to the coordinate dimension. In non-homogeneous collections, this will return the largest topological dimension of the contained objects.
geo:dimension
a rdf:Property, owl:DatatypeProperty ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "dimension"@en ;
skos:definition "The topological dimension of this geometric object, which
must be less than or equal to the coordinate dimension. In
non-homogeneous collections, this is the largest
topological dimension of the contained objects."@en ;
rdfs:domain geo:Geometry ;
rdfs:range xsd:integer ;
.8.7.2. Property: geo:coordinateDimension
The property geo:coordinateDimension is defined to link a Geometry object to the dimension of direct positions (coordinate tuples) used in the Geometry’s definition.
geo:coordinateDimension
a rdf:Property, owl:DatatypeProperty;
rdfs:isDefinedBy geo: ;
skos:prefLabel "coordinate dimension"@en ;
skos:definition "The number of measurements or axes needed to describe the
position of this Geometry in a coordinate system."@en ;
rdfs:domain geo:Geometry ;
rdfs:range xsd:integer ;
.8.7.3. Property: geo:spatialDimension
The property geo:spatialDimension is defined to link a Geometry object to the dimension of the spatial portion of the direct positions (coordinate tuples) used in its serializations. If the direct positions do not carry a measure coordinate, this will be equal to the coordinate dimension.
geo:spatialDimension
a rdf:Property, owl:DatatypeProperty;
rdfs:isDefinedBy geo: ;
skos:prefLabel "spatial dimension"@en ;
skos:definition "The number of measurements or axes needed to describe the
spatial position of this Geometry in a coordinate system."@en ;
rdfs:domain geo:Geometry ;
rdfs:range xsd:integer ;
.8.7.4. Property: geo:hasSpatialResolution
The property geo:hasSpatialResolution is defined to indicate the spatial resolution of the elements within a Geometry. Spatial resolution specifies the level of detail of a Geometry. It is the smallest distinguishable distance between adjacent coordinate sets. This property is not applicable to a point Geometry, because a point consists of a single coordinate set.
Since this property is defined for a geo:Geometry, all literal representations of that Geometry instance must have the same spatial resolution.
geo:hasSpatialResolution
a rdf:Property, owl:ObjectProperty;
rdfs:isDefinedBy geo: ;
skos:prefLabel "has spatial resolution"@en ;
skos:definition "The spatial resolution of a Geometry"@en ;
rdfs:domain geo:Geometry ;
.8.7.5. Property: geo:hasMetricSpatialResolution
The property geo:hasMetricSpatialResolution is similar to geo:hasSpatialResolution, except that the unit of resolution is always meter (the standard distance unit of the International System of Units).
geo:hasMetricSpatialResolution
a rdf:Property, owl:ObjectProperty;
rdfs:isDefinedBy geo: ;
skos:prefLabel "has spatial resolution in meters"@en ;
skos:definition "The spatial resolution of a Geometry in meters."@en ;
rdfs:domain geo:Geometry ;
rdfs:range xsd:double ;
.8.7.6. Property: geo:hasSpatialAccuracy
The property geo:hasSpatialAccuracy is applicable when a Geometry is used to represent a Feature. It is expressed as a distance that indicates the truthfulness of the positions (coordinates) that define the Geometry. In this case accuracy defines a zone surrounding each coordinate within which the real positions are known to be. The accuracy value defines this zone as a distance from the coordinate(s) in all directions (e.g. a line, a circle or a sphere, depending on spatial dimension).
geo:hasSpatialAccuracy
a rdf:Property, owl:ObjectProperty;
rdfs:isDefinedBy geo: ;
skos:prefLabel "has spatial accuracy"@en ;
skos:definition "The positional accuracy of the coordinates of a Geometry."@en ;
rdfs:domain geo:Geometry ;
.8.7.7. Property: geo:hasMetricSpatialAccuracy
The property geo:hasMetricSpatialAccuracy is similar to has spatial accuracy, but is easier to specify and use because the unit of distance is always meter (the standard distance unit of the International System of Units).
geo:hasMetricSpatialAccuracy
a rdf:Property, owl:ObjectProperty;
rdfs:isDefinedBy geo: ;
skos:prefLabel "has spatial accuracy in meters"@en ;
skos:definition "The positional accuracy of the coordinates of a Geometry in meters."@en ;
rdfs:domain geo:Geometry ;
rdfs:range xsd:double ;
.8.7.8. Property: geo:isEmpty
The property geo:isEmpty will indicate a Boolean object set to true if and only if the Geometry contains no information.
geo:isEmpty
a rdf:Property, owl:DatatypeProperty ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "is empty"@en ;
skos:definition "(true) if this geometric object is the empty Geometry. If
true, then this geometric object represents the empty point
set for the coordinate space."@en ;
rdfs:domain geo:Geometry ;
rdfs:range xsd:boolean ;
.8.7.9. Property: geo:isSimple
The property geo:isSimple will indicate a Boolean object set to true if and only if the Geometry contains no self-intersections, with the possible exception of its boundary.
geo:isSimple
a rdf:Property, owl:DatatypeProperty ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "is simple"@en ;
skos:definition "(true) if this geometric object has no anomalous geometric
points, such as self intersection or self tangency."@en ;
rdfs:domain geo:Geometry ;
rdfs:range xsd:boolean ;
.8.7.10. Property: geo:hasSerialization
The property geo:hasSerialization is defined to connect a Geometry with its text-based serialization (e.g., its WKT serialization).
geo:hasSerialization
a rdf:Property, owl:DatatypeProperty ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "has serialization"@en ;
skos:definition "Connects a Geometry object with its text-based serialization."@en ;
rdfs:domain geo:Geometry ;
rdfs:range rdfs:Literal ;
.|
Note
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this property is the generic property used to connect a Geometry with its serialization. GeoSPARQL also contains a number of sub properties of this property for connecting serializations of common types with geometries, for example as GeoJSON which can be used for GeoJSON [GEOJSON] literals. |
8.8. Geometry Serializations
This section establishes the Requirements class for representing Geometry data in RDF literals, according to different non-RDF systems.
GeoSPARQL presents specializations of the geo:hasSerialization property for indicating particular serializations and specialized datatype literals for containing them. It does not provide comprehensive definitions of their content since these are given in standards external to GeoSPARQL, all of which are referenced.
GeoSPARQL does present some Requirements for literal structure which extend the serialization-defining standards, for example the requirement to allow indications of spatial reference systems within WKT geometry representations.
GeoSPARQL’s expectation of RDF literal representations of geometry data is that it is related to the Simple Features Access (SFA) [OGCSFACA] [ISO19125-1] standard’s conceptualization of geometry which defines classes such as Point, Curve and Surface and specialized variants of them which it presents in a hierarchy. All SFA classes are represented in OWL in the Simple Features Vocabulary presented within GeoSPARQL as an independent profile element, see GeoSPARQL Standard structure.
Some geometry representation systems given here do not use the same terminology as SFA, in particular Discrete Global Grid Systems. To know the extent to which geometry literal representations listed here support SFA, or map to SFA, please see their definitions.
8.8.1. Well-Known Text
This section establishes the requirements for representing Geometry data in RDF based on Well-Known Text (WKT) as defined by Simple Features Access [OGCSFACA] [ISO19125-1]. It defines one RDFS Datatype: WKT Literal and one property, as WKT.
8.8.1.1. RDFS Datatype: geo:wktLiteral
The datatype geo:wktLiteral is used to contain the Well-Known Text (WKT) serialization of a Geometry.
geo:wktLiteral
a rdfs:Datatype ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "Well-known Text literal"@en ;
skos:definition "A Well-known Text serialization of a Geometry object."@en ;
.Req 14 All RDFS Literals of type |
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The following ABNF [IETF5234] syntax specification formally defines this literal:
wktLiteral ::= opt-iri-and-whitespace geometry-data
opt-iri-and-space = "<" IRI ">" LWSP / ""The token opt-iri-and-whitespace may be either an IRI and whitespace (spaces, tabs, newlines) or nothing (""), the token IRI (Internationalized Resource Identifier) is essentially a web address and is defined in [IETF3987] and the token LWSP, is one or more white space characters, as defined in [IETF5234]. geometry-data is the Well-Known Text representation of the Geometry, defined in [ISO13249].
In the absence of a leading spatial reference system IRI, the following spatial reference system IRI will be assumed: <http://www.opengis.net/def/crs/OGC/1.3/CRS84>. This IRI denotes WGS 84 longitude-latitude.
Req 15 The IRI |
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The OGC maintains a set of SRS IRIs under the http://www.opengis.net/def/crs/ namespace and IRIs from this set are recommended for use. However others may also be used, as long as they are valid IRIs.
Req 16 Coordinate tuples within |
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The example WKT Literal below encodes a point Geometry using the default WGS84 geodetic longitude-latitude spatial reference system:
"Point(-83.38 33.95)"^^<http://www.opengis.net/ont/geosparql#wktLiteral>A second example below encodes the same point as encoded in the example above but using a SRS identified by http://www.opengis.net/def/SRS/EPSG/0/4326: a WGS 84 geodetic latitude-longitude spatial reference system (note that this spatial reference system defines a different axis order):
"<http://www.opengis.net/def/crs/EPSG/0/4326> Point(33.95 -83.38)"^^<http://www.opengis.net/ont/geosparql#wktLiteral>Req 17 An empty RDFS Literal of type |
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8.8.1.2. Property: geo:asWKT
The property geo:asWKT is defined to link a Geometry with its WKT serialization.
Req 18 Implementations shall allow the RDF property |
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geo:asWKT
a rdf:Property, owl:DatatypeProperty ;
rdfs:subPropertyOf geo:hasSerialization ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "as WKT"@en ;
skos:definition "The WKT serialization of a Geometry."@en ;
rdfs:domain geo:Geometry ;
rdfs:range geo:wktLiteral ;
.8.8.1.3. Function: geof:asWKT
geof:asWKT (geom: ogc:geomLiteral): geo:wktLiteralThe function geof:asWKT converts geom to an equivalent WKT representation preserving the spatial reference system.
Req 19 Implementations shall support |
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8.8.2. Geography Markup Language
This section establishes a Requirements class for representing Geometry data in RDF based on GML as defined by the Geography Markup Language Encoding Standard [OGC07-036]. It defines one RDFS Datatype: GML Literal and one property, as GML.
8.8.2.1. RDFS Datatype: geo:gmlLiteral
The datatype geo:gmlLiteral is used to contain the Geography Markup Language (GML) serialization of a Geometry.
geo:gmlLiteral
a rdfs:Datatype ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "GML literal"@en ;
skos:definition "The datatype of GML literal values"@en ;
.Valid GML Literal instances are formed by encoding Geometry information as a valid element from the GML schema that implements a subtype of GM_Object. For example, in GML 3.2.1 this is every element directly or indirectly in the substitution group of the element {http://www.opengis.net/ont/gml/3.2}AbstractGeometry. In GML 3.1.1 and GML 2.1.2 this is every element directly or indirectly in the substitution group of the element {http://www.opengis.net/ont/gml}_Geometry.
Req 20 All |
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The example GML Literal below encodes a point Geometry in the WGS 84 geodetic longitude-latitude spatial reference system using GML version 3.2:
"""
<gml:Point
srsName=\"http://www.opengis.net/def/crs/OGC/1.3/CRS84\"
xmlns:gml=\"http://www.opengis.net/gml/3.2\">
<gml:pos>-83.38 33.95</gml:pos>
</gml:Point>
"""^^<http://www.opengis.net/ont/geosparql#gmlLiteral>Req 21 An empty |
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Req 22 Implementations shall document supported GML profiles. |
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8.8.2.2. Property: geo:asGML
The property geo:asGML is defined to link a Geometry with its GML serialization.
Req 23 Implementations shall allow the RDF property |
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geo:asGML
a rdf:Property ;
rdfs:subPropertyOf geo:hasSerialization ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "as GML"@en ;
skos:definition "The GML serialization of a Geometry."@en ;
rdfs:domain geo:Geometry ;
rdfs:range geo:gmlLiteral ;
.8.8.2.3. Function: geof:asGML
geof:asGML (geom: ogc:geomLiteral, gmlProfile: xsd:string): geo:gmlLiteralThe function geof:asGML converts geom to an equivalent GML representation defined by a gmlProfile version string preserving the coordinate reference system.
Req 24 Implementations shall support |
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8.8.3. GeoJSON
This section establishes a Requirements class for representing Geometry data in RDF based on Geographic JavaScript Object Notation (GeoJSON) as defined by Section 8.8.3. It defines one RDFS Datatype: GeoJSON Literal and one property, as GeoJSON.
8.8.3.1. RDFS Datatype: geo:geoJSONLiteral
The datatype geo:geoJSONLiteral is used to contain the GeoJSON serialization of a Geometry.
geo:geoJSONLiteral a rdfs:Datatype ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "GeoJSON Literal"@en ;
skos:definition "A GeoJSON serialization of a Geometry object."@en .Valid GeoJSON Literal instances are formed by encoding Geometry information as a Geometry object as defined in the GeoJSON specification [GEOJSON].
Req 25 All |
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Req 26 RDFS Literals of type |
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The example GeoJSON Literal below encodes a point Geometry using the default WGS84 geodetic longitude-latitude spatial reference system for Simple Features 1.0:
"""
{"type": "Point", "coordinates": [-83.38,33.95]}
"""^^<http://www.opengis.net/ont/geosparql#geoJSONLiteral>Req 27 An empty RDFS Literal of type |
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8.8.3.2. Property: geo:asGeoJSON
The property geo:asGeoJSON is defined to link a Geometry with its GeoJSON serialization.
Req 28 Implementations shall allow the RDF property |
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geo:asGeoJSON
a rdf:Property, owl:DatatypeProperty ;
rdfs:subPropertyOf geo:hasSerialization ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "as GeoJSON"@en ;
skos:definition "The GeoJSON serialization of a Geometry."@en ;
rdfs:domain geo:Geometry ;
rdfs:range geo:geoJSONLiteral ;
.8.8.3.3. Function: geof:asGeoJSON
geof:asGeoJSON (geom: ogc:geomLiteral): geo:geoJSONLiteralThe function geof:asGeoJSON converts geom to an equivalent GeoJSON representation. Coordinates are converted to the CRS84 coordinate system, the only valid coordinate system to be used in a GeoJSON literal.
Req 29 Implementations shall support |
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8.8.4. Keyhole Markup Language
This section establishes the Requirements class for representing Geometry data in RDF based on KML as defined by [OGCKML]. It defines one RDFS Datatype: KML Literal and one property, as KML.
8.8.4.1. RDFS Datatype: geo:kmlLiteral
The datatype geo:kmlLiteral is used to contain the Keyhole Markup Language (KML) serialization of a Geometry.
geo:kmlLiteral
a rdfs:Datatype ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "KML Literal"@en ;
skos:definition "A KML serialization of a Geometry object."@en ;
.Valid KML Literal instances are formed by encoding Geometry information as a Geometry object as defined in the KML specification [OGCKML].
Req 30 All |
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Req 31 RDFS Literals of type |
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The example KML Literal below encodes a point Geometry using the default WGS84 geodetic longitude-latitude spatial reference system for Simple Features 1.0:
"""
<Point xmlns=\"http://www.opengis.net/kml/2.2\">
<coordinates>-83.38,33.95</coordinates>
</Point>
"""^^<http://www.opengis.net/ont/geosparql#kmlLiteral>Req 32 An empty RDFS Literal of type |
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8.8.4.2. Property: geo:asKML
The property geo:asKML is defined to link a Geometry with its KML serialization.
Req 33 Implementations shall allow the RDF property |
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The property as KML is used to link a geometric element with its KML serialization.
geo:asKML
a rdf:Property, owl:DatatypeProperty;
rdfs:subPropertyOf geo:hasSerialization ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "as KML"@en ;
skos:definition "The KML serialization of a Geometry."@en ;
rdfs:domain geo:Geometry ;
rdfs:range geo:kmlLiteral ;
.8.8.4.3. Function: geof:asKML
geof:asKML (geom: ogc:geomLiteral): geo:kmlLiteralThe function geof:asKML converts geom to an equivalent KML representation. Coordinates are converted to the CRS84 coordinate system, the only valid coordinate system to be used in a KML literal.
Req 34 Implementations shall support |
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8.8.5. Discrete Global Grid System
This section establishes the Requirements class for representing Discrete Global Grid System (DGGS) Geometry data as RDF literals. The form of geometry data representation is specific to individual DGGS implementations: known DGGSes are not compatible or even very similar.
The Requirements class defines one RDFS Datatype
http://www.opengis.net/ont/geosparql#dggsLiteral and one property, http://www.opengis.net/ont/geosparql#asDGGS.
8.8.5.1. RDFS Datatype: geo:dggsLiteral
The datatype geo:dggsLiteral is used to contain the Discrete Global Grid System (DGGS) serialization of a Geometry.
geo:dggsLiteral
a rdfs:Datatype ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "DGGS Literal"@en ;
skos:definition "A textual serialization of a Discrete Global Grid System (DGGS) Geometry object."@en
.Valid DGGS Literal instances are formed by encoding Geometry information according to a specific DGGS implementation. The specific implementation should be indicated by use of a subclass of the geo:dggsLiteral datatype.
Req 35 All RDFS Literals of type |
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The following ABNF [IETF5234] syntax specification formally defines this literal:
dggsLiteral ::= iri-and-whitespace dggs-geomety-data
iri-and-whitespace = "<" IRI ">" LWSPThe token iri-and-whitespace is an IRI and whitespace. The token IRI (Internationalized Resource Identifier) is essentially a web address and is defined in [IETF3987]. The token LWSP is one or more whitespace characters, as defined in [IETF5234]. dggs-geometry-data is geometry data formulated according to the DGGS identified by IRI.
An example of a DGGS literal for the AusPIX DGGS could be:
"<https://w3id.org/dggs/auspix> CELL (R3234)"^^geo:dggsLiteralWhere AusPIX is identified with the IRI https://w3id.org/dggs/auspix and CELL (R3234) is the representation of a geometry according to AusPIX.
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Note
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What R3234 means, or the meaning of any other element within a DGGS' geometry data is not handled by GeoSPARQL, just as GeoPSARQL does not delve into the internals of other Geometry formats such as WKT or GeoJSON.
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Req 36 An empty RDFS Literal of type |
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The following ABNF [IETF5234] syntax specification formally defines this literal:
dggsLiteral ::= iri-and-space dggs-geometry-data
iri-and-whitespace = "<" IRI ">" LWSP / ""The tokens used above are as per the DGGS ABNF above.
8.8.5.2. Property: geo:asDGGS
The property geo:asDGGS is defined to link a Geometry with its DGGS serialization.
Req 37 Implementations shall allow the RDF property
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geo:asDGGS
a rdf:Property, owl:DatatypeProperty ;
rdfs:subPropertyOf geo:hasSerialization ;
rdfs:isDefinedBy geo: ;
skos:prefLabel "as DGGS"@en ;
skos:definition "A DGGS serialization of a Geometry."@en ;
rdfs:domain geo:Geometry ;
rdfs:range geo:dggsLiteral ;
.8.8.5.3. Function: geof:asDGGS
geof:asDGGS (geom: ogc:geomLiteral, specificDggsDatatype: xsd:anyURI): geo:DggsLiteralThe function geof:asDGGS converts geom to an equivalent DGGS representation, formulated according to the specific DGGS literal indicated by the IRI required to be present in the DGGS literal.
Req 38 Implementations shall support |
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8.9. Non-topological Query Functions
This Requirements class defines SPARQL functions for performing non-topological spatial operations.
Req 39 Implementations shall support the functions
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Req 40 Implementations shall support the functions
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Note
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The Requirements to support non-topological query functions for DGGS geometry literals are separated from the Requirements to support them for traditional geometry literals as it is expected that implementing these functions for DGGS literals will be significantly more difficult. This is due to the novelty of DGGS literals and thus the lack of existing software libraries for their manipulation. |
Req 41 Implementations shall support the functions of Requirement 39 for DGGS geometry literals as SPARQL extension functions, in a manner which is consistent with definitions of these functions in Simple Features [OGCSFACA] [ISO19125-1], for non-DGGS geometry literals. |
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Req 42 Implementations shall support the functions of Requirement 40 for DGGS geometry literals as SPARQL extension functions which are defined in this standard, for non-DGGS geometry literals. |
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Functions from this Requirements class are listed below, alphabetically.
8.9.1. Function notes
These notes apply to all of the following functions in this section.
An invocation of any of the following functions with invalid arguments produces an error. An invalid argument includes any of the following:
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An argument of an unexpected type
-
An invalid geometry literal value
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A non-fitting geometry type for the given function
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A geometry literal from a spatial reference system that is incompatible with the spatial reference system used for calculations
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An invalid unit IRI
A more detailed description of expected inputs and expected outputs of the given functions is shown in Annex B.
Unless otherwise stated in the function definition, the following behaviors should be followed by all SPARQL extension functions defined in the GeoSPARQL standard:
-
Functions returning a new geometry literal should follow the literal format of the first geometry literal input parameter. If no geometry literal input parameter is present, a WKT literal shall be returned.
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Functions returning a new geometry literal should follow the SRS defined in the literal format of the first geometry literal input parameter. If no geometry literal input parameter is present, a geometry result should be returned in the CRS84 SRS.
For further discussion of the effects of errors during FILTER evaluation, consult Section 17[10] of the SPARQL specification [SPARQL].
Note that returning values instead of raising an error serves as an extension mechanism of SPARQL.
SPARQL language extensions may provide additional associations between operators and operator functions; … No additional operator may yield a result that replaces any result other … . The consequence of this rule is that SPARQLFILTERs will produce at least the same intermediate bindings after applying aFILTERas an unextended implementation.
This extension mechanism enables GeoSPARQL implementations to simultaneously support multiple geometry serializations. For example, a system that supports WKT Literal serializations may also support GML Literal serializations and consequently would not raise an error if it encounters multiple geometry datatypes while processing a given query.
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Note
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Several non-topological query functions use a unit of measure IRI. See the Recommendation for specification of units of measurement. Also, the OGC has recommended units of measure vocabularies for use, see the OGC Definitions Server[12]. |
8.9.2. Function: geof:metricArea
geof:metricArea (geom: ogc:geomLiteral): xsd:doubleThe function geof:metricArea returns the area of geom in square meters. Must return zero for all geometry types other than Polygon. This function is similar to geof:area but does not need a specification of measurement unit.
8.9.3. Function: geof:area
geof:area (geom: ogc:geomLiteral, units: xsd:anyURI): rdf:ResourceThe function geof:area returns the area of geom. Must return zero for all geometry types other than Polygon. This function is similar to geof:metricArea, which does not need a specification of measurement unit.
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Note
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See the Recommendation for specification of units of measurement. |
8.9.4. Function: geof:boundary
geof:boundary (geom: ogc:geomLiteral): ogc:geomLiteralThe function geof:boundary returns the closure of the boundary of geom. Calculations are in the spatial reference system of geom.
8.9.5. Function: geof:boundingCircle
geof:boundingCircle (geom: ogc:geomLiteral): ogc:geomLiteralThe function geof:boundingCircle returns the minimum bounding circle around geom. Calculations are in the spatial reference system of geom.
8.9.6. Function: geof:metricBuffer
geof:metricBuffer (geom: ogc:geomLiteral,
radius: xsd:double): ogc:geomLiteralThe function geof:metricBuffer returns a geometric object that represents all Points whose distance from geom is less than or equal to the radius measured in meters. Calculations are in the coordinate reference system of geom. This function is similar to geof:buffer, but does not need a specification of measurement unit.
8.9.7. Function: geof:buffer
geof:buffer (geom: ogc:geomLiteral,
radius: xsd:double,
units: xsd:anyURI): ogc:geomLiteralThe function geof:buffer returns a geometric object that represents all Points whose distance from geom is less than or equal to the radius measured in units. Calculations are in the spatial reference system of geom. This function is similar to geof:metricBuffer, which does not need a specification of measurement unit.
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Note
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See the Recommendation for specification of units of measurement. |
8.9.8. Function: geof:centroid
geof:centroid (geom: ogc:geomLiteral): ogc:geomLiteralThe function geof:centroid returns the mathematical centroid of geom. The centroid point does not have to be part of the surface it is derived from.
8.9.9. Function: geof:convexHull
geof:convexHull (geom: ogc:geomLiteral): ogc:geomLiteralThe function geof:convexHull returns a geometric object that represents all Points in the convex hull of geom. Calculations are in the spatial reference system of geom.
8.9.10. Function: geof:concaveHull
geof:concaveHull (geom: ogc:geomLiteral): ogc:geomLiteralThe function geof:concaveHull returns a geometric object that represents all Points in the concave hull of geom. Calculations are in the spatial reference system of geom. Various implementers use parameters to calculate a concave hull. As such, two implementations may return different results from their concave hull functions for the same geometry. Implementers should make clear any default values used to calculate a concave hull in their documentation.
8.9.11. Function: geof:coordinateDimension
geof:coordinateDimension (geom: ogc:geomLiteral): xsd:integerThe function geof:coordinateDimension returns the coordinate dimension of geom.
8.9.12. Function: geof:difference
geof:difference (geom1: ogc:geomLiteral,
geom2: ogc:geomLiteral): ogc:geomLiteralThe function geof:difference returns a geometric object that represents all Points in the set difference of geom1 with geom2. Calculations are in the spatial reference system of geom1.
8.9.13. Function: geof:dimension
geof:dimension (geom: ogc:geomLiteral): xsd:integerThe function geof:dimensions returns the dimension of geom. In non-homogeneous geometry collections, this will return the largest topological dimension of the contained objects.
8.9.14. Function: geof:metricDistance
geof:metricDistance (geom1: ogc:geomLiteral,
geom2: ogc:geomLiteral): xsd:doubleThe function geof:metricDistance returns the shortest distance in meters between any two Points in the two geometric objects. Calculations are in the coordinate reference system of geom1. This function is similar to geof:distance, but does not need a specification of measurement unit.
8.9.15. Function: geof:distance
geof:distance (geom1: ogc:geomLiteral,
geom2: ogc:geomLiteral,
units: xsd:anyURI): xsd:doubleThe function geof:distance returns the shortest distance in units between any two Points in the two geometric objects. Calculations are in the spatial reference system of geom1. This function is similar to geof:metricDistance, which does not need a specification of measurement unit.
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Note
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See the Recommendation for specification of units of measurement. |
8.9.16. Function: geof:envelope
geof:envelope (geom: ogc:geomLiteral): ogc:geomLiteralThe function geof:envelope returns the minimum bounding box - a rectangle - of geom. Calculations are in the spatial reference system of geom.
8.9.17. Function: geof:geometryN
geof:geometryN (geom: ogc:geomLiteral, geomindex: xsd:integer): ogc:geomLiteralThe function geof:geometryN returns the nth geometry of geom if it is a GeometryCollection that is defined in a literal type (such as in the case of a sf:GeometryCollection) or geom if it is a Geometry. This function is not applicable to the type geo:GeometryCollection, as elements in geo:GeometryCollection are not guaranteed to be ordered.
8.9.18. Function: geof:geometryType
geof:geometryType (geom: ogc:geomLiteral): xsd:anyURIThe function geof:geometryType returns the URI of the subtype of Geometry of which this geometric object is an member. No attempt to reconcile different geometry subtypes across all support literals need be made.
8.9.19. Function: geof:getSRID
geof:getSRID (geom: ogc:geomLiteral): xsd:anyURIThe function geof:getSRID returns the spatial reference system IRI for geom.
8.9.20. Function: geof:intersection
geof:intersection (geom1: ogc:geomLiteral,
geom2: ogc:geomLiteral): ogc:geomLiteralThe function geof:intersection returns a geometric object that represents all Points in the intersection of geom1 with geom2. Calculations are in the spatial reference system of geom1.
8.9.21. Function: geof:is3D
geof:is3D (geom: ogc:geomLiteral): xsd:booleanThe function geof:is3D Returns true if geom has z coordinate values.
8.9.22. Function: geof:isEmpty
geof:isEmpty (geom: ogc:geomLiteral): xsd:booleanThe function geof:isEmpty returns true if geom is an empty geometry, i.e. contains no coordinates.
8.9.23. Function: geof:isMeasured
geof:isMeasured (geom: ogc:geomLiteral): xsd:booleanThe function geof:isMeasured returns true if geom has m coordinate values.
8.9.24. Function: geof:isSimple
geof:isSimple (geom: ogc:geomLiteral): xsd:booleanThe function geof:isSimple returns true if geom is a simple geometry, i.e. has no anomalous geometric points, such as self intersection or self tangency.
8.9.25. Function: geof:metricLength
geof:metricLength (geom: ogc:geomLiteral): xsd:doubleThe function geof:metricLength returns the length of geom in meters. The longest length from any one dimension is returned. This is for example the length of a line from its beginning point to its endpoint or the length of the boundary of a polygon. This function is similar to geof:length but does not need a specification of measurement unit.
8.9.26. Function: geof:length
geof:length (geom: ogc:geomLiteral, units: xsd:anyURI): xsd:doubleThe function geof:length returns the length of geom. The longest length from any one dimension is returned. This function is similar to geof:metricLength, which does not need a specification of measurement unit.
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Note
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See the Recommendation for specification of units of measurement. |
8.9.27. Function: geof:maxX
geof:maxX (geom: ogc:geomLiteral): xsd:doubleThe function geof:maxX returns the maximum X coordinate for geom.
8.9.28. Function: geof:maxY
geof:maxY (geom: ogc:geomLiteral): xsd:doubleThe function geof:maxY returns the maximum Y coordinate for geom.
8.9.29. Function: geof:maxZ
geof:maxZ (geom: ogc:geomLiteral): xsd:doubleThe function geof:maxZ returns the maximum Z coordinate for geom.
8.9.30. Function: geof:minX
geof:minX (geom: ogc:geomLiteral): xsd:doubleThe function geof:minX returns the minimum X coordinate for geom.
8.9.31. Function: geof:minY
geof:minY (geom: ogc:geomLiteral): xsd:doubleThe function geof:minY returns the minimum Y coordinate for geom.
8.9.32. Function: geof:minZ
geof:minZ (geom: ogc:geomLiteral): xsd:doubleThe function geof:minZ returns the minimum Z coordinate for geom.
8.9.33. Function: geof:numGeometries
geof:numGeometries (geom: ogc:geomLiteral): xsd:integerThe function geof:numGeometries returns the number of geometries of geom.
8.9.34. Function: geof:perimeter
geof:perimeter (geom: ogc:geomLiteral, unit: xsd:anyURI): xsd:doubleThe function geof:perimeter returns the perimeter of geom in the unit specified by the unit parameter for areal geometries. For non-areal geometries the result is equivalent to geof:hasLength.
8.9.35. Function: geof:metricPerimeter
geof:metricPerimeter (geom: ogc:geomLiteral): xsd:doubleThe function geof:metricPerimeter returns the perimeter of geom. It is similar to the function geof:perimeter, but always returns the result in meters.
8.9.36. Function: geof:spatialDimension
geof:spatialDimension (geom: ogc:geomLiteral): xsd:integerThe function geof:spatialDimension returns the spatial dimension of geom.
8.9.37. Function: geof:symDifference
geof:symDifference (geom1: ogc:geomLiteral,
geom2: ogc:geomLiteral): ogc:geomLiteralThe function geof:symDifference returns a geometric object that represents all Points in the set symmetric difference of geom1 with geom2. Calculations are in the spatial reference system of geom1.
8.9.38. Function: geof:transform
geof:transform (geom: ogc:geomLiteral, srsIRI: xsd:anyURI): ogc:geomLiteralThe function geof:transform converts geom to a spatial reference system defined by srsIRI. The function raises an error if a transformation is not mathematically possible.
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Note
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We recommend that implementers use the same literal type as a result of this function as the type of the input literal. |
8.9.39. Function: geof:union
geof:union (geom1: ogc:geomLiteral,
geom2: ogc:geomLiteral): ogc:geomLiteralThis function geof:union returns a geometric object that represents all Points in the union of geom1 with geom2. Calculations are in the spatial reference system of geom1.
Req 43 Implementations shall support |
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8.10. Spatial Aggregate Functions
This clause defines SPARQL functions for performing spatial aggregations of data.
Req 44 Implementations shall support
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8.10.1. Function: geof:aggBoundingBox
geof:aggBoundingBox (geom: ogc:geomLiteral): ogc:geomLiteralThe function geof:aggBoundingBox calculates a minimum bounding box - rectangle - of the set of given geometries.
8.10.2. Function: geof:aggBoundingCircle
geof:aggBoundingCircle (geom: ogc:geomLiteral): ogc:geomLiteralThe function geof:aggBoundingCircle calculates a minimum bounding circle of the set of given geometries.
8.10.3. Function: geof:aggCentroid
geof:aggCentroid (geom: ogc:geomLiteral): ogc:geomLiteralThe function geof:aggCentroid calculates the centroid of the set of given geometries.
8.10.4. Function: geof:aggConcaveHull
geof:aggConcaveHull (geom: ogc:geomLiteral, targetPercent: xsd:double): ogc:geomLiteralThe function geof:aggConcaveHull calculates the concave hull of the set of given geometries.
8.10.5. Function: geof:aggConvexHull
geof:aggConvexHull (geom: ogc:geomLiteral): ogc:geomLiteralThe function geof:aggConvexHull calculates the convex hull of the set of given geometries.
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Note
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This function is similar in name to geof:convexHull used to calculate the convex hull of just one geometry. |
8.10.6. Function: geof:aggUnion
geof:aggUnion (geom: ogc:geomLiteral): ogc:geomLiteralThe function geof:aggUnion calculates the union of the set of given geometries.
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Note
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This function is similar in name to geof:union used to calculate the union of just two geometries. |
9. Geometry Topology Extension
This clause establishes the Geometry Topology Extension parameterized Requirements class with base IRI /req/geometry-topology-extension, which defines a collection of topological query functions that operate on geometry literals. These Requirements are parameterized to give implementations flexibility in the topological relation families and geometry serializations that they choose to support. These Requirements have a single corresponding conformance class Geometry Topology Extension, with IRI /conf/geometry-topology-extension.
The Dimensionally Extended Nine Intersection Model (DE-9IM) [DE-9IM] has been used to define the relation tested by the query functions introduced in this section. Each query function is associated with a defining DE-9IM intersection pattern. Possible pattern values are:
-
-1(empty) -
0,1,2,T(true) ={0, 1, 2} -
F(false) ={-1} -
*(don’t care) ={-1, 0, 1, 2}
In the following descriptions, the notation X/Y is used to denote applying a spatial relation to geometry types X and Y (i.e., x relation y where x is of type X and y is of type Y). The symbol P is used for 0-dimensional geometries (e.g. points). The symbol L is used for 1- dimensional geometries (e.g. lines), and the symbol A is used for 2-dimensional geometries (e.g. polygons). Consult the Simple Features specification [OGCSFACA] [ISO19125-1] for a more detailed description of DE-9IM intersection patterns.
9.1. Parameters
-
relation_family: Specifies the set of topological spatial relations to support.
-
serialization: Specifies the serialization standard to use for geometry literals.
-
version: Specifies the version of the serialization format used.
9.2. Common Query Functions
Req 45 Implementations shall support
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geof:relate (geom1: ogc:geomLiteral,
geom2: ogc:geomLiteral,
pattern-matrix: xsd:string): xsd:booleanReturns true if the spatial relationship between geom1 and geom2 corresponds to one with acceptable values for the specified pattern-matrix. Otherwise, this function returns false. pattern-matrix represents a DE-9IM intersection pattern consisting of T (true) and F (false) values. The spatial reference system for geom1 is used for spatial calculations.
9.3. Simple Features Relation Family
This clause establishes Requirements for the Simple Features relation family.
Req 46 Implementations shall support
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Boolean query functions defined for the Simple Features relation family, along with their associated DE-9IM intersection patterns, are shown in Table 6 below. Multi-row intersection patterns should be interpreted as a logical OR of each row. Each function accepts two arguments (geom1 and geom2) of the geometry literal serialization type specified by serialization and version. Each function returns an xsd:boolean value of true if the specified relation exists between geom1 and geom2 and returns false otherwise. In each case, the spatial reference system of geom1 is used for spatial calculations.
| Query Function | Defining DE-9IM Intersection Pattern |
|---|---|
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9.4. Egenhofer Relation Family
This clause establishes Requirements for the Egenhofer relation family. Consult references [FORMAL] and [CATEG] for a more detailed discussion of Egenhofer relations.
Req 47 Implementations shall support
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Boolean query functions defined for the Egenhofer relation family, along with their associated DE-9IM intersection patterns, are shown in Table 7 below. Multi-row intersection patterns should be interpreted as a logical OR of each row. Each function accepts two arguments (geom1 and geom2) of the geometry literal serialization type specified by serialization and version. Each function returns an xsd:boolean value of true if the specified relation exists between geom1 and geom2 and returns false otherwise. In each case, the spatial reference system of geom1 is used for spatial calculations.
| Query Function | Defining DE-9IM Intersection Pattern |
|---|---|
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9.5. RCC8 Relation Family
This clause establishes Requirements for the RCC8 relation family. Consult references [QUAL] and [LOGIC] for a more detailed discussion of RCC8 relations.
Req 48 Implementations shall support
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Boolean query functions defined for the RCC8 relation family, along with their associated DE-9IM intersection patterns, are shown in Table 8 below. Each function accepts two arguments (geom1 and geom2) of the geometry literal serialization type specified by serialization and version. Each function returns an xsd:boolean value of true if the specified relation exists between geom1 and geom2 and returns false otherwise. In each case, the spatial reference system of geom1 is used for spatial calculations.
| Query Function | Defining DE-9IM Intersection Pattern |
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10. RDFS Entailment Extension
This clause establishes the RDFS Entailment Extension parameterized Requirements class with base IRI /req/rdfs-entailment-extension, which defines a mechanism for matching implicitly-derived RDF triples in GeoSPARQL queries. This class is parameterized to give implementations flexibility in the topological relation families and geometry types that they choose to support. These Requirements have a single corresponding conformance class RDFS Entailment Extension, with IRI /conf/rdfs-entailment-extension.
10.1. Parameters
-
relation_family: Specifies the set of topological spatial relations to support.
-
serialization: Specifies the serialization standard to use for geometry literals.
-
version: Specifies the version of the serialization format used.
10.2. Common Requirements
The basic mechanism for supporting RDFS entailment has been defined by the W3C SPARQL 1.1 RDFS Entailment Regime [SPARQLENT].
Req 49 Basic graph pattern matching shall use the semantics defined by the RDFS Entailment Regime [SPARQLENT]. |
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10.3. WKT Serialization
This section establishes the requirements for representing geometry data in RDF based on WKT as defined by Simple Features [OGCSFACA] [ISO19125-1].
10.3.1. Geometry Class Hierarchy
The Simple Features specification presents a geometry class hierarchy. It is straightforward to represent this class hierarchy in RDFS and OWL by constructing IRIs for geometry classes using the following pattern: http://www.opengis.net/ont/sf#{geometry class} and by asserting appropriate rdfs:subClassOf statements. The Simple Features Vocabulary resource within GeoSPARQL 1.1 (sibling resource to this specification) does this. The following list gives the class hierarchy with each indented item being a subclass of the item in the line above. The class hierarchy starts with GeoSPARQL’s geo:Geometry class of which sf:Geometry is a subclass:
geo:Geometry
sf:Geometry
sf:Curve
sf:LineString
sf:Line
sf:LinearRing
sf:GeometryCollection
sf:MultiCurve
sf:MultiLineString
sf:MultiPoint
sf:MultiSurface
sf:MultiPolygon
sf:Point
sf:Surface
sf:Polygon
sf:Envelope
sf:Triangle
sf:PolyhedralSurface
sf:TINThe following example RDF snippet below encodes the Simple Features vocabulary Polygon class:
sf:Polygon
a rdfs:Class, owl:Class ;
rdfs:isDefinedBy <http://www.opengis.net/ont/sf> ;
skos:prefLabel "Polygon"@en ;
rdfs:subClassOf sf:Surface ;
skos:definition "A planar surface defined by 1 exterior boundary and 0 or
more interior boundaries"@en ;
.Req 50 Implementations shall support graph patterns involving terms from an RDFS/OWL class hierarchy of geometry types consistent with the one in the specified version of Simple Features [OGCSFACA] [ISO19125-1]. |
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10.4. GML Serialization
This section establishes Requirements for representing geometry data in RDF based on GML as defined by Geography Markup Language Encoding Standard [OGC07-036].
10.4.1. Geometry Class Hierarchy
An RDF/OWL class hierarchy can be generated from the GML schema that implements GM_Object by constructing IRIs for geometry classes using the following pattern: http://www.opengis.net/ont/gml#{GML Element} and by asserting appropriate rdfs:subClassOf statements.
The example RDF snippet below encodes the Polygon class from GML 3.2.
gml:Polygon
a rdfs:Class, owl:Class ;
skos:prefLabel "Polygon"@en ;
rdfs:subClassOf gml:SurfacePatch ;
skos:definition "A planar surface defined by 1 exterior boundary and 0 or
more interior boundaries."@en ;
.Req 51 Implementations shall support graph patterns involving terms from an RDFS/OWL class hierarchy of geometry types consistent with the GML schema that implements |
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11. Query Rewrite Extension
This clause establishes the Query Rewrite Extension parameterized Requirements class with base IRI /req/query-rewrite-extension, which has a single corresponding conformance class Query Rewrite Extension, with IRI /conf/query-rewrite-extension. These Requirements define a set of RIF rules [RIF] that use topological extension functions defined in Clause 9 to establish the existence of direct topological predicates defined in Clause 7. One possible implementation strategy is to transform a given query by expanding a triple pattern involving a direct spatial predicate into a series of triple patterns and an invocation of the corresponding extension function as specified in the RIF rule.
The following rule specified using the RIF Core Dialect [RIFCORE] and shown in Presentation Syntax is used as a template to describe rules in the remainder of this clause. ogc:relation is used as a placeholder for the spatial relation IRIs defined in Clause 7, and ogc:function is used as a placeholder for the spatial functions defined in Clause 9. ogc:asGeomLiteral is used to indicate one of the properties that link geo:Geometry instances to serialisations, such as geo:asWKT or geo:asGeoJSON. The variables ?so1 & ?so2 represent geo:SpatialObject instances (either geo:Feature or geo:Geometry instances), ?g1 & ?g2 geo:Geometry instances only and ?g1Serial & ?g2Serial represent geo:Geometry instance serializations, e.g. geo:asWKT etc. literals.
Forall ?so1 ?so2 ?g1 ?g2 ?g1Serial ?g2Serial (
?so1[ogc:relation->?so2] :- Or (
And (
# feature - feature rule
?so1[geo:hasDefaultGeometry->?g1]
?so2[geo:hasDefaultGeometry->?g2]
?g1[ogc:asGeomLiteral->?g1Serial]
?g2[ogc:asGeomLiteral->?g2Serial]
External(ogc:function(?g1Serial, ?g2Serial))
)
And (
# feature - geometry rule
?so1[geo:hasDefaultGeometry->?g1]
?g1[ogc:asGeomLiteral->?g1Serial]
?so2[ogc:asGeomLiteral->?g2Serial]
External(ogc:function(?g1Serial, ?g2Serial))
)
And (
# geometry - feature rule
?so1[ogc:asGeomLiteral->?g1Serial]
?so2[geo:hasDefaultGeometry->?g2]
?g2[ogc:asGeomLiteral->?g2Serial]
External(ogc:function(?g1Serial, ?g2Serial))
)
And (
# geometry - geometry rule
?so1[ogc:asGeomLiteral->?g1Serial]
?so2[ogc:asGeomLiteral->?g2Serial]
External(ogc:function(?g1Serial, ?g2Serial))
)
)
)11.1. Parameters
-
relation_family: Specifies the set of topological spatial relations to support.
-
serialization: Specifies the serialization standard to use for geometry literals.
-
version: Specifies the version of the serialization format used.
11.2. Simple Features Relation Family
This clause defines Requirements for the Simple Features relation family. Table 9 specifies the function and property substitutions for each rule in the Simple Features relation family.
Req 52 Basic graph pattern matching shall use the semantics defined by the RIF Core Entailment Regime [SPARQLENT] for the RIF rules [RIFCORE]
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| Rule | ogc:relation | ogc:function |
|---|---|---|
11.3. Egenhofer Relation Family
This clause defines Requirements for the Egenhofer relation family. Table 10 specifies the function and property substitutions for each rule in the Egenhofer relation family.
Req 53 Basic graph pattern matching shall use the semantics defined by the RIF Core Entailment Regime [SPARQLENT] for the RIF rules [RIFCORE]
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| Rule | ogc:relation | ogc:function |
|---|---|---|
11.4. RCC8 Relation Family
This clause defines Requirements for the RCC8 relation family. Table 11 specifies the function and property substitutions for each rule in the RCC8 relation family.
Req 54 Basic graph pattern matching shall use the semantics defined by the RIF Core Entailment Regime [SPARQLENT] for the RIF rules [RIFCORE]
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| Rule | ogc:relation | ogc:function |
|---|---|---|
11.5. Special Considerations
The applicability of GeoSPARQL rules in certain circumstances has intentionally been left undefined.
The first situation arises for triple patterns with unbound predicates. Consider the query pattern below:
{ my:feature1 ?p my:feature2 }When using a query transformation strategy, this triple pattern could invoke none of the GeoSPARQL rules or all of the rules. Implementations are free to support either of these alternatives.
The second situation arises when supporting GeoSPARQL rules in the presence of RDFS Entailment. The existence of a topological relation (possibly derived from a GeoSPARQL rule) can entail other RDF triples. For example, if geo:sfOverlaps has been defined as an rdfs:subPropertyOf the property my:overlaps, and the RDF triple my:feature1 geo:sfOverlaps my:feature2 has been derived from a GeoSPARQL rule, then the RDF triple my:feature1 my:overlaps my:feature2 can be entailed. Implementations may support such entailments but are not required to.
12. Future Work
Many future extensions of this standard are possible and, since the release of GeoSPARQL 1.0, many extensions have been made.
The GeoSPARQL 1.1 release incorporates many additions requested of the GeoSPARQL 1.0 Standard, including the use of particular new serializations: where GeoSPARQL 1.0 supported GML & WKT, GeoSPARQL 1.1 also supports GeoJSON, KML and a generic DGGS literal. GeoSPARQL 1.1 also supports spatial scalar properties.
Plans for future GeoSPARQL releases have been suggested but won’t be articulated here. Instead they will be discussed and decided upon by the OGC GeoSPARQL Standards Working Group and related groups. Readers of this document are encouraged to seek out those groups' lists of issues and standards change requests rather than looking for ideas here that will surely age badly.
Annex A - Abstract Test Suite (normative)
A.0 Overview
This Annex lists tests for the Conformance Classes defined in the main body sections of this Specification with links to their Requirements and test purpose method and type. Conformance classes may be used to signify the compatibility of a given implementation to parts of the GeoSPARQL standard. They may be stated as part of a SPARQL 1.1 Service Description [SPARQLSERVDESC] .
A.1 Conformance Class: Core
Conformance Class IRI: /conf/core
A.1.1 SPARQL
A.1.1.1 /conf/core/sparql-protocol
Requirement: /req/core/sparql-protocol
Implementations shall support the SPARQL Query Language for RDF [SPARQL], the SPARQL Protocol for RDF [SPARQLPROT] and the SPARQL Query Results XML Format [SPARQLRESX].
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that the implementation accepts SPARQL queries and returns the correct results in the correct format, according to the SPARQL Query Language for RDF, the SPARQL Protocol for RDF and SPARQL Query Results XML Format W3C specifications.
-
Reference: Section 4.1.4
-
Test Type: Capabilities
A.1.2 RDF Classes & Properties
A.1.2.1 /conf/core/spatial-object-class
Requirement: /req/core/spatial-object-class
Implementations shall allow the RDFS class geo:SpatialObject to be used in SPARQL graph
patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving
geo:SpatialObjectreturn the correct result on a test dataset. -
Reference: Section 6.2.1
-
Test Type: Capabilities
A.1.2.2 /conf/core/feature-class
Requirement: /req/core/feature-class
Implementations shall allow the RDFS class geo:Feature to be used in SPARQL graph patterns.
-
Test purpose: check conformance with this requirement
-
Test method: verify that queries involving
geo:Featurereturn the correct result on a test dataset. -
Reference: Section 6.2.2
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Test Type: Capabilities
A.1.2.3 /conf/core/spatial-object-collection-class
Requirement: /req/core/spatial-object-collection-class
Implementations shall allow the RDFS class geo:SpatialObjectCollection to be used in SPARQL graph
patterns.
-
Test purpose: check conformance with this requirement
-
Test method: verify that queries involving
geo:SpatialObjectCollectionreturn the correct result on a test dataset. -
Reference: Section 6.2.3
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Test Type: Capabilities
A.1.2.4 /conf/core/feature-collection-class
Requirement: /req/core/feature-collection-class
Implementations shall allow the RDFS class geo:FeatureCollection to be used in SPARQL graph
patterns.
-
Test purpose: check conformance with this requirement
-
Test method: verify that queries involving
geo:FeatureCollectionreturn the correct result on a test dataset. -
Reference: Section 6.2.4
-
Test Type: Capabilities
A.1.2.5 /conf/core/spatial-object-properties
Implementations shall allow the properties
geo:hasSize,
geo:hasMetricSize,
geo:hasLength,
geo:hasMetricLength,
geo:hasPerimeterLength,
geo:hasMetricPerimeterLength,
geo:hasArea,
geo:hasMetricArea,
geo:hasVolume and
geo:hasMetricVolume.
to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving these properties return the correct result for a test dataset.
-
Reference: Section 6.3
-
Test Type: Capabilities
A.2 Conformance Class: Topology Vocabulary Extension
Conformance Class IRI: /conf/topology-vocab-extension
A.2.1 Simple Features Relation Family
A.2.1.1 /conf/topology-vocab-extension/sf-spatial-relations
Requirement: /req/topology-vocab-extension/sf-spatial-relations
Implementations shall allow the properties
geo:sfEquals,
geo:sfDisjoint,
geo:sfIntersects,
geo:sfTouches,
geo:sfCrosses,
geo:sfWithin,
geo:sfContains and
geo:sfOverlaps
to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving these properties return the correct result for a test dataset.
-
Reference: Section 7.2
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Test Type: Capabilities
A.2.2 Egenhofer Relation Family
A.2.2.1 /conf/topology-vocab-extension/eh-spatial-relations
Requirement: /req/topology-vocab-extension/eh-spatial-relations
Implementations shall allow the properties
geo:ehEquals,
geo:ehDisjoint,
geo:ehMeet,
geo:ehOverlap,
geo:ehCovers,
geo:ehCoveredBy,
geo:ehInside and
geo:ehContains
to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving these properties return the correct result for a test dataset.
-
Reference: Section 7.3
-
Test Type: Capabilities
A.2.3 RCC8 Relation Family
A.2.3.1 /conf/topology-vocab-extension/rcc8-spatial-relations
Requirement: /req/topology-vocab-extension/rcc8-spatial-relations
Implementations shall allow the properties
geo:rcc8eq,
geo:rcc8dc,
geo:rcc8ec,
geo:rcc8po,
geo:rcc8tppi,
geo:rcc8tpp,
geo:rcc8ntpp,
geo:rcc8ntppi
to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving these properties return the correct result for a test dataset.
-
Reference: Section 7.4
-
Test Type: Capabilities
A.3 Conformance Class: Geometry Extension
This Conformance Class applies to non-DGGS geometries. See A.3.DGGS Conformance Class: Geometry Extension - DGGS for DGGS geometries.
Conformance Class IRI: /conf/geometry-extension
A.3.1 Tests for all Serializations except DGGS
A.3.1.1 /conf/geometry-extension/geometry-class
Requirement: /req/geometry-extension/geometry-class
Implementations shall allow the RDFS class
geo:Geometry
to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving
geo:Geometryreturn the correct result on a test dataset -
Reference: Section 8.6.1
-
Test Type: Capabilities
A.3.1.2 /conf/geometry-extension/geometry-collection-class
Requirement: /req/geometry-extension/geometry-collection-class
Implementations shall allow the RDFS class Geometry Collection to be used in SPARQL graph patterns.
-
Test purpose: check conformance with this requirement
-
Test method: verify that queries involving Geometry Collection return the correct result on a test dataset
-
Reference: Section 8.6.2
-
Test Type: Capabilities
A.3.1.3 /conf/geometry-extension/feature-properties
Requirement: /req/geometry-extension/feature-properties
Implementations shall allow the properties
geo:hasGeometry,
geo:hasDefaultGeometry,
geo:hasLength,
geo:hasArea,
geo:hasVolume
geo:hasCentroid,
geo:hasBoundingBox and
geo:hasSpatialResolution
to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving these properties return the correct result for a test dataset.
-
Reference: Section 6.4
-
Test Type: Capabilities
A.3.1.4 /conf/geometry-extension/geometry-properties
Requirement: /req/geometry-extension/geometry-properties
Implementations shall allow the properties
geo:dimension,
geo:coordinateDimension,
geo:spatialDimension,
geo:isEmpty,
geo:isSimple and
geo:hasSerialization
to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving these properties return the correct result for a test dataset.
-
Reference: Section 8.7
-
Test Type: Capabilities
A.3.1.5 /conf/geometry-extension/query-functions
Requirement: /req/geometry-extension/query-functions
Implementations shall support the functions
geof:distance,
geof:buffer,
geof:intersection,
geof:union,
geof:isEmpty,
geof:isSimple,
geof:area,
geof:length,
geof:numGeometries,
geof:geometryN,
geof:transform,
geof:dimension,
geof:difference,
geof:symDifference,
geof:envelope and
geof:boundary
as SPARQL extension functions, consistent with the definitions of their corresponding functions in Simple Features [OGCSFACA] [ISO19125-1] (distance, buffer, intersection, union, isEmpty, isSimple, area, length, numGeometries, geometryN, transform, dimension, difference, symDifference, envelope and boundary respectively) and other attached definitions and also
geof:maxX,
geof:maxY,
geof:maxZ,
geof:minX,
geof:minY and
geof:minZ
SPARQL extension functions.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving each of the following functions returns the correct result for a test dataset when using the specified serialization and version:
geof:distance,geof:buffer,geof:intersection,geof:union,geof:isEmpty,geof:isSimple,geof:area,geof:length,geof:numGeometries,geof:geometryN,geof:transform,geof:dimension,geof:difference,geof:symDifference,geof:envelopeandgeof:boundary. -
Reference: Section 8.9
-
Test Type: Capabilities
A.3.1.6 /conf/geometry-extension/srid-function
Requirement: /req/geometry-extension/srid-function
Implementations shall support get SRID as a SPARQL extension function.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a SPARQL query involving the get SRID function returns the correct result for a test dataset when using the specified serialization and version.
-
Reference: Section 8.9.19
-
Test Type: Capabilities
A.3.1.7 /conf/geometry-extension/sa-functions
Requirement: /req/geometry-extension/sa-functions
Implementations shall support
geof:aggBoundingBox,
geof:aggBoundingCircle,
geof:aggCentroid,
geof:aggConcaveHull,
geof:aggConvexHull and
geof:aggUnion
as a SPARQL extension functions.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving these functions return the correct result for a test dataset.
-
Reference: Section 8.10
-
Test Type: Capabilities
A.3.2 WKT Serialization
A.3.2.1 /conf/geometry-extension/wkt-literal
Requirement: /req/geometry-extension/wkt-literal
All RDFS Literals of type geo:wktLiteral shall consist of an optional IRI identifying the coordinate reference system and a required Well Known Text (WKT) description of a geometric value. Valid geo:wktLiteral instances are formed by either a WKT string as defined in [ISO13249] or by concatenating a valid absolute IRI, as defined in [IETF3987], enclose in angled brackets (< & >) followed by a single space (Unicode U+0020 character) as a separator, and a WKT string as defined in [ISO13249].
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving WKT Literal values return the correct result for a test dataset.
-
Reference: Section 8.8.1.1
-
Test Type: Capabilities
A.3.2.2 /conf/geometry-extension/wkt-literal-default-srs
Requirement: /req/geometry-extension/wkt-literal-default-srs
The IRI <http://www.opengis.net/def/crs/OGC/1.3/CRS84> shall be assumed as the spatial reference system for geo:wktLiteral instances that do not specify an explicit spatial reference system IRI.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving WKT Literal values without an explicit encoded SRS IRI return the correct result for a test dataset.
-
Reference: Section 8.8.1.1
-
Test Type: Capabilities
A.3.2.3 /conf/geometry-extension/wkt-axis-order
Requirement: /req/geometry-extension/wkt-axis-order
Coordinate tuples within WKT Literal instances shall be interpreted using the axis order defined in the SRS used.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving WKT Literal values return the correct result for a test dataset.
-
Reference: Section 8.8.1.1
-
Test Type: Capabilities
A.3.2.4 /conf/geometry-extension/wkt-literal-empty
Requirement: /req/geometry-extension/wkt-literal-empty
An empty RDFS Literal of type WKT Literal shall be interpreted as an empty geometry.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving empty WKT Literal values return the correct result for a test dataset.
-
Reference: Section 8.8.1.1
-
Test Type: Capabilities
A.3.2.5 /conf/geometry-extension/geometry-as-wkt-literal
Requirement: /req/geometry-extension/geometry-as-wkt-literal
Implementations shall allow the RDF property geo:asWKT to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving the
geo:asWKTproperty return the correct result for a test dataset. -
Reference: Section 8.8.1.2
-
Test Type: Capabilities
A.3.2.6 /req/geometry-extension/asWKT-function
Requirement: /req/geometry-extension/asWKT-function
Implementations shall support geof:asWKT, as a SPARQL extension function
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving the
geof:asWKTfunction returns the correct result for a test dataset when using the specified serialization and version. -
Reference: Section 8.8.1.3
-
Test Type: Capabilities
A.3.3 GML Serialization
A.3.3.1 /conf/geometry-extension/gml-literal
Requirement: /req/geometry-extension/gml-literal
All geo:gmlLiteral instances shall consist of a valid element from the GML schema that implements a subtype of GM_Object as defined in [OGC 07-036].
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving
geo:gmlLiteralvalues return the correct result for a test dataset. -
Reference: Section 8.8.2.1
-
Test Type: Capabilities
A.3.3.2 /conf/geometry-extension/gml-literal-empty
Requirement: /req/geometry-extension/gml-literal-empty
An empty geo:gmlLiteral shall be interpreted as an empty geometry.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving empty
geo:gmlLiteralvalues return the correct result for a test dataset. -
Reference: Section 8.8.2.1
-
Test Type: Capabilities
A.3.3.3 /conf/geometry-extension/gml-profile
Requirement: /req/geometry-extension/gml-profile
Implementations shall document supported GML profiles.
-
Test purpose: Check conformance with this requirement
-
Test method: Examine the implementation’s documentation to verify that the supported GML profiles are documented.
-
Reference: Section 8.8.2.1
-
Test Type: Documentation
A.3.3.4 /conf/geometry-extension/geometry-as-gml-literal
Requirement: /req/geometry-extension/geometry-as-gml-literal
Implementations shall allow the RDF property geo:asGML to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving the
geo:asGMLproperty return the correct result for a test dataset. -
Reference: Section 8.8.2.2
-
Test Type: Capabilities
A.3.3.5 /req/geometry-extension/asGML-function
Requirement: /req/geometry-extension/asGML-function
Implementations shall support geof:asGML, as a SPARQL extension function
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving the
geof:asGMLfunction returns the correct result for a test dataset when using the specified serialization and version. -
Reference: Section 8.8.2.3
-
Test Type: Capabilities
A.3.4 GeoJSON Serialization
A.3.4.1 /req/geometry-extension/geojson-literal
Requirement: /req/geometry-extension/geojson-literal
All geo:geoJSONLiteral instances shall consist of valid JSON that conforms to the GeoJSON specification [GEOJSON]
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving
geo:geoJSONLiteralvalues return the correct result for a test dataset. -
Reference: Section 8.8.3.1
-
Test Type: Capabilities
A.3.4.2 /req/geometry-extension/geojson-literal-srs
Requirement: /req/geometry-extension/geojson-literal-default-srs
The IRI <http://www.opengis.net/def/crs/OGC/1.3/CRS84> shall be assumed as the SRS for geo:geoJSONLiteral instances that do not specify an explicit SRS IRI.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving
geo:geoJSONLiteralvalues without an explicit encoded SRS IRI return the correct result for a test dataset. -
Reference: Section 8.8.3.1
-
Test Type: Capabilities
A.3.4.3 /req/geometry-extension/geojson-literal-empty
Requirement: /req/geometry-extension/geojson-literal-empty
An empty geo:geoJSONLiteral shall be interpreted as an empty geometry.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving empty
geo:geoJSONLiteralvalues return the correct result for a test dataset. -
Reference: Section 8.8.3.1
-
Test Type: Capabilities
A.3.4.4 /req/geometry-extension/geometry-as-geojson-literal
Requirement: /req/geometry-extension/geometry-as-geojson-literal
Implementations shall allow the RDF property geo:asGeoJSON to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving the
geo:asGeoJSONproperty return the correct result for a test dataset. -
Reference: Section 8.8.3.2
-
Test Type: Capabilities
A.3.4.5 /req/geometry-extension/asGeoJSON-function
Requirement: /req/geometry-extension/asGeoJSON-function
Implementations shall support geof:asGeoJSON, as a SPARQL extension function
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving the
geof:asGeoJSONfunction returns the correct result for a test dataset when using the specified serialization and version. -
Reference: Section 8.8.3.3
-
Test Type: Capabilities
A.3.5 KML Serialization
A.3.5.1 /req/geometry-extension/kml-literal
Requirement: /req/geometry-extension/kml-literal
All geo:kmlLiteral instances shall consist of a valid element from the KML schema that implements a kml:AbstractObjectGroup as defined in [OGCKML].
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving
geo:kmlLiteralvalues return the correct result for a test dataset. -
Reference: Section 8.8.4.1
-
Test Type: Capabilities
A.3.5.2 /req/geometry-extension/kml-literal-srs
Requirement: /req/geometry-extension/kml-literal-default-srs
The IRI <http://www.opengis.net/def/crs/OGC/1.3/CRS84> shall be assumed as the SRS for geo:kmlLiteral instances that do not specify an explicit SRS IRI.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving
geo:kmlLiteralvalues without an explicit encoded SRS IRI return the correct result for a test dataset. -
Reference: Section 8.8.4.1
-
Test Type: Capabilities
A.3.5.3 /req/geometry-extension/kml-literal-empty
Requirement: /req/geometry-extension/kml-literal-empty
An empty geo:kmlLiteral shall be interpreted as an empty geometry.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving empty
geo:kmlLiteralvalues return the correct result for a test dataset. -
Reference: Section 8.8.4.1
-
Test Type: Capabilities
A.3.5.4 /req/geometry-extension/geometry-as-kml-literal
Requirement: /req/geometry-extension/geometry-as-kml-literal
Implementations shall allow the RDF property geo:asKML to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving the
geo:asKMLproperty return the correct result for a test dataset. -
Reference: Section 8.8.4.2
-
Test Type: Capabilities
A.3.5.5 /req/geometry-extension/asKML-function
Requirement: /req/geometry-extension/asKML-function
Implementations shall support geof:asKML, as a SPARQL extension function
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving the
geof:asKMLfunction returns the correct result for a test dataset when using the specified serialization and version. -
Reference: Section 8.8.4.3
-
Test Type: Capabilities
A.3.6 DGGS Serialization
A.3.6.1 /req/geometry-extension/dggs-literal
Requirement: /req/geometry-extension/dggs-literal
All RDFS Literals of type geo:dggsLiteral shall consist of an IRI identifying the specific DGGS and a representation of the DGGS geometry data. The IRI shall be enclosed in angled brackets (< & >) followed by whitespace as a separator, and then the DGGS geometry data, formulated according to the identified DGGS.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving empty
geo:dggsLiteralvalues return the correct result for a test dataset. -
Reference: Section 8.8.5.1
-
Test Type: Capabilities
A.3.6.2 /req/geometry-extension/dggs-literal-empty
Requirement: /req/geometry-extension/dggs-literal-empty
An empty RDFS Literal of type geo:dggsLiteral, shall be interpreted as an empty geo:Geometry.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving empty
geo:dggsLiteralvalues return the correct result for a test dataset. -
Reference: Section 8.8.5.1
-
Test Type: Capabilities
A.3.6.3 /req/geometry-extension/geometry-as-dggs-literal
Requirement: /req/geometry-extension/geometry-as-dggs-literal
Implementations shall allow the RDF property geo:asDGGS to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving the
geo:asDGGSproperty return the correct result for a test dataset. -
Reference: Section 8.8.5.2
-
Test Type: Capabilities
A.3.6.4 /req/geometry-extension/asDGGS-function
Requirement: /req/geometry-extension/asDGGS-function
Implementations shall support geof:asDGGS, as a SPARQL extension function.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving the
geof:asDGGSfunction returns the correct result for a test dataset when using the specified serialization and version. -
Reference: Section 8.8.5.3
-
Test Type: Capabilities
A.3.DGGS Conformance Class: Geometry Extension - DGGS
This conformance Class applies only to DGGS geometries. See A.3 Conformance Class: Geometry Extension for other geometries.
Conformance Class IRI: /conf/geometry-extension
A.3.DGGS.1 Tests for DGGS Serializations
A.3.DGGS.1.1 /conf/geometry-extension/geometry-class
Requirement: /req/geometry-extension/geometry-class
Implementations shall allow the RDFS class
geo:Geometry
to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving
geo:Geometryreturn the correct result on a test dataset -
Reference: Section 8.6.1
-
Test Type: Capabilities
A.3.DGGS.1.2 /conf/geometry-extension/geometry-collection-class
Requirement: /req/geometry-extension/geometry-collection-class
Implementations shall allow the RDFS class
geo:GeometryCollection
to be used in SPARQL graph patterns.
-
Test purpose: check conformance with this requirement
-
Test method: verify that queries involving
geo:GeometryCollectionreturn the correct result on a test dataset -
Reference: Section 8.6.2
-
Test Type: Capabilities
A.3.DGGS.1.3 /conf/geometry-extension/feature-properties
Requirement: /req/geometry-extension/feature-properties
Implementations shall allow the properties
geo:hasGeometry,
geo:hasDefaultGeometry,
geo:hasLength,
geo:hasArea,
geo:hasVolume
geo:hasCentroid,
geo:hasBoundingBox and
geo:hasSpatialResolution
to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving these properties return the correct result for a test dataset.
-
Reference: Section 6.4
-
Test Type: Capabilities
A.3.DGGS.1.4 /conf/geometry-extension/geometry-properties
Requirement: /req/geometry-extension/geometry-properties
Implementations shall allow the properties
geo:dimension,
geo:spatialDimension,
geo:isEmpty,
geo:isSimple and
geo:hasSerialization
to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving these properties return the correct result for a test dataset.
-
Reference: Section 8.7
-
Test Type: Capabilities
A.3.DGGS.1.5 /conf/geometry-extension/query-functions
Requirement: /req/geometry-extension/query-functions
Implementations shall support the functions
geof:distance,
geof:buffer,
geof:intersection,
geof:union,
geof:isEmpty,
geof:isSimple,
geof:area,
geof:length,
geof:numGeometries,
geof:geometryN,
geof:transform,
geof:dimension,
geof:difference,
geof:symDifference,
geof:envelope and
geof:boundary
as SPARQL extension functions
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving each of the following functions returns the correct result for a test dataset when using the specified serialization and version:
geof:distance,geof:buffer,geof:intersection,geof:union,geof:isEmpty,geof:isSimple,geof:area,geof:length,geof:numGeometries,geof:geometryN,geof:transform,geof:dimension,geof:difference,geof:symDifference,geof:envelopeandgeof:boundary. -
Reference: Section 8.9
-
Test Type: Capabilities
A.3.DGGS.1.6 /conf/geometry-extension/srid-function
Requirement: /req/geometry-extension/srid-function
Implementations shall support
geof:getSRID
as a SPARQL extension function.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a SPARQL query involving the
geof:getSRIDfunction returns the correct result for a test dataset when using the specified serialization and version. -
Reference: Section 8.9.19
-
Test Type: Capabilities
A.3.DGGS.1.7 /conf/geometry-extension/sa-functions
Requirement: /req/geometry-extension/sa-functions
Implementations shall support
geof:boundingBox,
geof:boundingCircle,
geof:centroid,
geof:concatLines,
geof:concaveHull,
geof:convexHull and
geof:union2
as a SPARQL extension functions.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving these functions return the correct result for a test dataset.
-
Reference: Section 8.10
-
Test Type: Capabilities
A.3.DGGS.2 DGGS Serialization
A.3.DGGS.2.1 /req/geometry-extension/dggs-literal
Requirement: /req/geometry-extension/dggs-literal
All RDFS Literals of type geo:dggsLiteral shall consist of a DGGS geometry serialization formulated according to a specific DGGS literal type identified by a datatype specializing this generic datatype.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries do not use use this datatype but instead use specializations of it.
-
Reference: Section 8.8.5.1
-
Test Type: Capabilities
A.3.DGGS.2.2 /req/geometry-extension/dggs-literal-empty
Requirement: /req/geometry-extension/dggs-literal-empty
An empty geo:dggsLiteral shall be interpreted as an empty geometry.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving empty
geo:dggsLiteralvalues return the correct result for a test dataset. -
Reference: Section 8.8.5.1
-
Test Type: Capabilities
A.3.DGGS.2.3 /req/geometry-extension/geometry-as-dggs-literal
Requirement: /req/geometry-extension/geometry-as-dggs-literal
Implementations shall allow the RDF property geo:asDGGS to be used in SPARQL graph patterns.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving the
geo:asDGGSproperty return the correct result for a test dataset. -
Reference: Section 8.8.5.2
-
Test Type: Capabilities
A.3.DGGS.2.4 /req/geometry-extension/asDGGS-function
Requirement: /req/geometry-extension/asDGGS-function
Implementations shall support geof:asDGGS, as a SPARQL extension function
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving the
geof:asDGGSfunction returns the correct result for a test dataset when using the specified serialization and version. -
Reference: Section 8.8.5.3
-
Test Type: Capabilities
A.4 Conformance Class: Geometry Topology Extension
Conformance Class IRI: /conf/geometry-topology-extension
A.4.1 Tests for all relation families
A.4.1.1 /conf/geometry-topology-extension/relate-query-function
Requirement: /req/geometry-topology-extension/relate-query-function
Implementations shall support
geof:relate
as a SPARQL extension function, consistent with the relate operator defined in Simple Features [OGCSFACA] [ISO19125-1].
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving the
geof:relatefunction returns the correct result for a test dataset when using the specified serialization and version. -
Reference: Section 9.2
-
Test Type: Capabilities
A.4.2 Simple Features Relation Family
A.4.2.1 /conf/geometry-topology-extension/sf-query-functions
Requirement: /req/geometry-topology-extension/sf-query-functions
Implementations shall support
geof:sfEquals,
geof:sfDisjoint,
geof:sfIntersects,
geof:sfTouches,
geof:sfCrosses,
geof:sfWithin,
geof:sfContains and
geof:sfOverlaps
as SPARQL extension functions, consistent with their corresponding DE-9IM intersection patterns, as defined by Simple Features [OGCSFACA] [ISO19125-1].
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving each of the following functions returns the correct result for a test dataset when using the specified serialization and version:
geof:sfEquals,geof:sfDisjoint,geof:sfIntersects,geof:sfTouches,geof:sfCrosses,geof:sfWithin,geof:sfContains,geof:sfOverlaps. -
Reference: Section 7.2
-
Test Type: Capabilities
A.4.3 Egenhofer Relation Family
A.4.3.1 /conf/geometry-topology-extension/eh-query-functions
Requirement: /req/geometry-topology-extension/eh-query-functions
Implementations shall support
geof:ehEquals,
geof:ehDisjoint,
geof:ehMeet,
geof:ehOverlap,
geof:ehCovers,
geof:ehCoveredBy,
geof:ehInside and
geof:ehContains
as SPARQL extension functions, consistent with their corresponding DE-9IM intersection patterns, as defined by Simple Features [OGCSFACA] [ISO19125-1].
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving each of the following functions returns the correct result for a test dataset when using the specified serialization and version:
geof:ehEquals,geof:ehDisjoint,geof:ehMeet,geof:ehOverlap,geof:ehCovers,geof:ehCoveredBy,geof:ehInside,geof:ehContains. -
Reference: Section 7.3
-
Test Type: Capabilities
A.4.4 RCC8 Relation Family
A.4.4.1 /conf/geometry-topology-extension/rcc8-query-functions
Requirement: /req/geometry-topology-extension/rcc8-query-functions
Implementations shall support
geof:rcc8eq,
geof:rcc8dc,
geof:rcc8ec,
geof:rcc8po,
geof:rcc8tppi,
geof:rcc8tpp,
geof:rcc8ntpp and
geof:rcc8ntppi
as SPARQL extension functions, consistent with their corresponding DE-9IM intersection patterns, as defined by Simple Features [OGCSFACA] [ISO19125-1].
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving each of the following functions returns the correct result for a test dataset when using the specified serialization and version:
geof:rcc8eq,geof:rcc8dc,geof:rcc8ec,geof:rcc8po,geof:rcc8tppi,geof:rcc8tpp,geof:rcc8ntpp,geof:rcc8ntppi. -
Reference: Section 7.4
-
Test Type: Capabilities
A.5 Conformance Class: RDFS Entailment Extension
Conformance Class IRI: /conf/rdfs-entailment-extension
A.5.1 Tests for all implementations
A.5.1.1 /conf/rdfsentailmentextension/bgp-rdfs-ent
Requirement: /req/rdfs-entailment-extension/bgp-rdfs-ent
Basic graph pattern matching shall use the semantics defined by the RDFS Entailment Regime [SPARQLENT].
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving entailed RDF triples returns the correct result for a test dataset using the specified serialization, version and relation_family.
-
Reference: Section 10.2
-
Test Type: Capabilities
A.5.2 WKT Serialization
A.5.2.1 /conf/rdfs-entailment-extension/wkt-geometry-types
Requirement: /req/rdfs-entailment-extension/wkt-geometry-types
Implementations shall support graph patterns involving terms from an RDFS/OWL class hierarchy of geometry types consistent with the one in the specified version of Simple Features [OGCSFACA] [ISO19125-1].
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving WKT Geometry types returns the correct result for a test dataset using the specified version of Simple Features.
-
Reference: Section 10.3.1
-
Test Type: Capabilities
A.5.3 GML Serialization
A.5.3.1 /conf/rdfs-entailment-extension/gml-geometry-types
Requirement: /req/rdfs-entailment-extension/gml-geometry-types
Implementations shall support graph patterns involving terms from an RDFS/OWL class hierarchy of geometry types consistent with the GML schema that implements GM_Object using the specified version of GML [OGC07-036].
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that a set of SPARQL queries involving GML Geometry types returns the correct result for a test dataset using the specified version of GML.
-
Reference: Section 10.4.1
-
Test Type: Capabilities
A.6 Conformance Class: Query Rewrite Extension
Conformance Class IRI: /conf/query-rewrite-extension
A.6.1 Simple Features Relation Family
A.6.1.1 /conf/query-rewrite-extension/sf-query-rewrite
Requirement: /req/query-rewrite-extension/sf-query-rewrite
Basic graph pattern matching shall use the semantics defined by the RIF Core Entailment Regime [SPARQLENT] for the RIF rules [RIFCORE]
geor:sfEquals,
geor:sfDisjoint,
geor:sfIntersects,
geor:sfTouches,
geor:sfCrosses,
geor:sfWithin,
geor:sfContains and
geor:sfOverlaps.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving the following query transformation rules return the correct result for a test dataset when using the specified serialization and version:
geor:sfEquals,geor:sfDisjoint,geor:sfIntersects,geor:sfTouches,geor:sfCrosses,geor:sfWithin,geor:sfContainsandgeor:sfOverlaps. -
Reference: Section 7.2
-
Test Type: Capabilities
A.6.2 Egenhofer Relation Family
A.6.2.1 /conf/query-rewrite-extension/eh-query-rewrite
Requirement: /req/query-rewrite-extension/eh-query-rewrite
Basic graph pattern matching shall use the semantics defined by the RIF Core Entailment Regime [SPARQLENT] for the RIF rules [RIFCORE]
geor:ehEquals,
geor:ehDisjoint,
geor:ehMeet,
geor:ehOverlap,
geor:ehCovers,
geor:ehCoveredBy,
geor:ehInside and
geor:ehContains.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving the following query transformation rules return the correct result for a test dataset when using the specified serialization and version:
geor:ehEquals,geor:ehDisjoint,geor:ehMeet,geor:ehOverlap,geor:ehCovers,geor:ehCoveredBy,geor:ehInside,geor:ehContains. -
Reference: Section 7.3
-
Test Type: Capabilities
A.6.3 RCC8 Relation Family
A.6.3.1 /conf/query-rewrite-extension/rcc8-query-rewrite
Requirement: /req/query-rewrite-extension/rcc8-query-rewrite
Basic graph pattern matching shall use the semantics defined by the RIF Core Entailment Regime [SPARQLENT] for the RIF rules [RIFCORE]
geor:rcc8eq,
geor:rcc8dc,
geor:rcc8ec,
geor:rcc8po,
geor:rcc8tppi,
geor:rcc8tpp,
geor:rcc8ntpp and
geor:rcc8ntppi.
-
Test purpose: Check conformance with this requirement
-
Test method: Verify that queries involving the following query transformation rules return the correct result for a test dataset when using the specified serialization and version:
geor:rcc8eq,geor:rcc8dc,geor:rcc8ec,geor:rcc8po,geor:rcc8tppi,geor:rcc8tpp,geor:rcc8ntpp,geor:rcc8ntppi. -
Reference: Section 7.4
-
Test Type: Capabilities
Annex B - Functions Summary (normative)
B.0 Overview
This annex summarizes all the functions defined in GeoSPARQL, providing descriptions of their parameters and return types.
The value ogc:geomLiteral indicates any one of the specific geometry serializations datatypes defined in this Specification, for example geo:wktLiteral.
The geometry subtypes - Polygon, Point, CellList etc. - are the Simple Features specification [OGCSFACA] [ISO19125-1] or DGGS types, as implemented by the various geometry serialization specifications referenced here. See Section 8.8 for the individual specification references.
B.1 Functions Summary Table
Simple Features Functions |
||||
Function |
Input Datatypes |
Input Subtypes |
Output Datatype |
Output Subtype |
2x ogc:geomLiteral |
1x Polygon, 1x Geometry |
|||
2x ogc:geomLiteral |
1x Point or LineString, 1 x LineString or Polygon |
|||
2x ogc:geomLiteral |
2x Geometry |
|||
2x ogc:geomLiteral |
2x Geometry |
|||
2x ogc:geomLiteral |
2x Polygon |
|||
2x ogc:geomLiteral |
2x Point or 2x LineString or 2x Polygon |
|||
2x ogc:geomLiteral |
2x Geometry but not Point |
|||
2x ogc:geomLiteral |
1x Geometry, 1x Polygon |
|||
Egenhofer Functions |
||||
Function |
Input Datatypes |
Input Subtypes |
Output Datatype |
Output Subtype |
2x ogc:geomLiteral |
1x Polygon, 1x Geometry |
|||
2x ogc:geomLiteral |
1x Polygon, 1x Geometry |
|||
2x ogc:geomLiteral |
1x Polygon, 1x Geometry |
|||
2x ogc:geomLiteral |
2x Geometry |
|||
2x ogc:geomLiteral |
2x Geometry |
|||
2x ogc:geomLiteral |
2x Geometry but not Point |
|||
2x ogc:geomLiteral |
2x Geometry |
|||
2x ogc:geomLiteral |
2x Geometry |
|||
Region Connection Calculus Functions |
||||
Function |
Input Datatypes |
Input Subtypes |
Output Datatype |
Output Subtype |
2x ogc:geomLiteral |
2x Polygon |
|||
2x ogc:geomLiteral |
2x Polygon |
|||
2x ogc:geomLiteral |
2x Polygon |
|||
2x ogc:geomLiteral |
2x Polygon |
|||
2x ogc:geomLiteral |
2x Polygon |
|||
2x ogc:geomLiteral |
2x Polygon |
|||
2x ogc:geomLiteral |
2x Polygon |
|||
2x ogc:geomLiteral |
2x Polygon |
|||
Spatial Aggregate Functions |
||||
Function |
Input Datatypes |
Input Subtypes |
Output Datatype |
Output Subtype |
1 or more ogc:geomLiteral |
ogc:geomLiteral |
square Polygon (not DGGS), CellList (DGGS) |
||
1 or more ogc:geomLiteral |
ogc:geomLiteral |
Polygon (not DGGS) CellList (DGGS) |
||
1 or more ogc:geomLiteral |
ogc:geomLiteral |
Point (not DGGS), Cell (DGGS) |
||
1 or more ogc:geomLiteral |
ogc:geomLiteral |
Polygon (not DGGS), CellList (DGGS) |
||
1 or more ogc:geomLiteral |
ogc:geomLiteral |
Polygon (not DGGS), CellList (DGGS) |
||
1 or more ogc:geomLiteral |
ogc:geomLiteral |
Polygon (not DGGS), CellList (DGGS) |
||
Non-topological Query Functions |
||||
Function |
Input Datatypes |
Input Subtypes |
Output Datatype |
Output Subtype |
1x ogc:geomLiteral |
Polygon |
|||
1x ogc:geomLiteral |
Polygon |
|||
1x ogc:geomLiteral |
Geometry |
ogc:geomLiteral |
LineString (not DGGS), OrderedCellList (DGGS) |
|
1x ogc:geomLiteral, 1x xsd:double, 1x xsd:anyURI |
any |
ogc:geomLiteral |
(Multi)Polygon (not DGGS), CellList (DGGS) |
|
1x ogc:geomLiteral |
Geometry |
ogc:geomLiteral |
LineString (not DGGS) |
|
1x ogc:geomLiteral |
Geometry |
|||
2x ogc:geomLiteral |
2x Geometry |
ogc:geomLiteral |
(Multi)Polygon (not DGGS), CellList (DGGS) |
|
1x ogc:geomLiteral |
Geometry |
|||
2x ogc:geomLiteral, 1x xsd:anyURI |
2x Geometry |
|||
2x ogc:geomLiteral, 1x xsd:anyURI |
2x Geometry |
|||
1x ogc:geomLiteral, 1x xsd:anyURI |
Geometry |
ogc:geomLiteral |
(Multi)Polygon (not DGGS), CellList (DGGS) |
|
1x ogc:geomLiteral |
GeometryCollection (not DGGS) |
|||
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
2x ogc:geomLiteral |
2x Geometry |
ogc:geomLiteral |
Polygon (not DGGS), CellList (DGGS) |
|
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry (not DGGS) |
|||
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
2x ogc:geomLiteral |
2x Geometry |
ogc:geomLiteral |
(Multi)Polygon (not DGGS), CellList DGGS) |
|
1x ogc:geomLiteral, 1x xsd:anyURI |
Geometry |
ogc:geomLiteral |
Geometry |
|
2x ogc:geomLiteral |
2x Geometry |
ogc:geomLiteral |
Polygon (not DGGS), CellList (DGGS) |
|
Serialization Functions |
||||
Function |
Input Datatypes |
Input Subtypes |
Output Datatype |
Output Subtype |
1x ogc:geomLiteral |
Geometry |
geo:dggsLiteral |
||
1x ogc:geomLiteral |
Geometry |
geo:geoJSONLiteral |
||
1x ogc:geomLiteral, 1x xsd:string |
Geometry |
geo:gmlLiteral |
||
1x ogc:geomLiteral |
Geometry |
geo:kmlLiteral |
||
1x ogc:geomLiteral |
Geometry |
geo:wktLiteral |
||
Extent Functions |
||||
Function |
Input Datatypes |
Input Subtypes |
Output Datatype |
Output Subtype |
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
1x ogc:geomLiteral |
Geometry |
|||
Other Functions |
||||
Function |
Input Datatypes |
Input Subtypes |
Output Datatype |
Output Subtype |
2x ogc:geomLiteral |
||||
B.2 GeoSPARQL to SFA Functions Mapping
The following table indicates which GeoSPARQL non-topological query functions map to Simple Features Access ([OGCSFACA] [ISO19125-1]) functions and in which GeoSPARQL version the functions are defined.
Where the Simple Features Access function has the same name as the GeoSPARQL function, 'x' is recorded.
| GeoSPARQL Function | in 1.0 | in 1.1 | SFA |
|---|---|---|---|
metricArea |
x |
Area |
|
area |
x |
Area |
|
AsBinary |
|||
asWKT* |
x |
x |
AsText |
boundary |
x |
x |
Boundary |
buffer |
x |
x |
Buffer |
Centroid |
|||
convexHull |
x |
x |
ConvexHull |
coordinateDimension |
x |
||
difference |
x |
x |
Difference |
dimension |
x |
Dimension |
|
metricDistance |
x |
Distance |
|
distance |
x |
x |
Distance |
EndPoint |
|||
envelope |
x |
x |
Envelope |
geometryN |
x |
GeometryN |
|
geometryType |
x |
GeometryType |
|
getSRID |
x |
x |
SRID |
InteriorRingN |
|||
intersection |
x |
x |
Intersection |
is3D |
x |
||
IsClosed |
|||
isEmpty |
x |
IsEmpty |
|
isMeasured |
x |
||
IsRing |
|||
isSimple |
x |
IsSimple |
|
metricLength |
x |
Length |
|
length |
x |
Length |
|
maxX |
x |
||
maxY |
x |
||
maxZ |
x |
||
minX |
x |
||
minY |
x |
||
minZ |
x |
||
numGeometries |
x |
NumGeometries |
|
NumInteriorRing |
|||
NumPoints |
|||
perimeterLength |
x |
||
perimeter |
x |
||
PointN |
|||
PointOnSurface |
|||
spatialDimension |
x |
||
StartPoint |
|||
symDifference |
x |
x |
SymDifference |
transform |
x |
||
union |
x |
x |
Union |
X |
|||
Y |
* GeoSPARQL’s asWKT is only a partial implementation of asText since asWKT only returns WKT, not textual geometry literal data in general.
Annex C - GeoSPARQL Examples (informative)
C.0 Overview
This Annex provides examples of the GeoSPARQL ontology and functions. In addition to these, extended examples are provided separately by the GeoSPARQL 1.1 profile. See the GeoSPARQL Standard structure for the link to those examples.
C.1 RDF Examples
This Section illustrates GeoSPARQL ontology modelling with extended examples.
C.1.1 Classes
C.1.1.1 SpatialObject
The SpatialObject class is defined in Section 6.2.1.
C.1.1.1.1 Basic use
Basic use (as per the example in the class definition)
eg:x
a geo:SpatialObject ;
skos:prefLabel "Object X";
.|
Note
|
It is unlikely that users of GeoSPARQL will create many instances of geo:SpatialObject as its two more concrete subclasses, geo:Feature & geo:Geometry, are more directly relatable to real-world phenomena and use.
|
C.1.1.1.2 Size Properties
The "size" properties - geo:hasSize,
geo:hasMetricSize,
geo:hasLength,
geo:hasMetricLength,
geo:hasPerimeterLength,
geo:hasMetricPerimeterLength,
geo:hasArea,
geo:hasMetricArea,
geo:hasVolume and
geo:hasMetricVolume - are all applicable to instances of geo:SpatialObject although, as per the note in the section above, they are likely to be used with geo:Feature & geo:Geometry instances.
@prefix qudt: <http://qudt.org/schema/qudt/> .
@prefix unit: <http://qudt.org/vocab/unit/> .
eg:moreton-island
a geo:SpatialObject ;
skos:prefLabel "Moreton Island" ;
rdfs:seeAlso "https://en.wikipedia.org/wiki/Moreton_Island"^^xsd:anyURI ;
geo:hasPerimeterLength [
qudt:numericValue "92.367"^^xsd:float ;
qudt:unit unit:KiloM ;
];
geo:hasMetricPerimeterLength "92367"^^xsd:double ;
.Here a spatial object, Moreton Island, has the distance of its coastline given with two properties: geo:hasPerimeterLength & geo:hasMetricPerimeterLength. The object for the first is a Blank Node with a QUDT value property of 92.367 and a QUDT unit property of unit:KiloM (kilometre). The object for the second is the literal 92367 (a double) which is, by the property’s definition, a number of metres.
The use of the Quantities, Units, Dimensions and Types (QUDT) ontology[13] and its qudt:numericValue & qudt:unit is just one of many possible ways to convey the value of geo:hasPerimeterLength and any subproperty of geo:hasSize.
C.1.1.2 Feature
The Feature class is defined in Section 6.2.2.
C.1.1.2.1 Basic use
eg:x
a geo:Feature ;
skos:prefLabel "Feature X" ;
.Here a Feature is declared and given a preferred label.
C.1.1.2.2 A Feature related to a Geometry
eg:x
a geo:Feature ;
skos:prefLabel "Feature X" ;
geo:hasGeometry [
geo:asWKT "MULTIPOLYGON (((149.06016 -35.23610, 149.06062 -35.23604, ... , 149.06016 -35.23610)))"^^geo:wktLiteral ;
] ;
.Here a geo:Feature is declared, given a preferred label and a Geometry for that geo:Feature is indicated with the use of geo:hasGeometry. The Geometry indicated is described using a Well-Known Text literal value, indicated by the property geo:asWKT and the literal type geo:wktLiteral.
C.1.1.2.3 Feature with Geometry and size (area)
eg:x
a geo:Feature ;
skos:prefLabel "Feature X" ;
geo:hasGeometry [
geo:asWKT "MULTIPOLYGON (((149.06016 -35.23610, 149.06062 -35.23604, ... , 149.06016 -35.23610)))"^^geo:wktLiteral ;
] ;
geo:hasMetricArea "8.9E4"^^xsd:double ;
.This example and the example below (B 1.1.2.4) show the same geo:Feature, but with a different specification of its area. This example shows the recommended way to express size: by using a subproperty of geo:hasMetricSize (in this case, [Property: geo:MetricArea]). These subproperties have fixed units based on meter (the unit of distance in the International System of Units).
C.1.1.2.4 Feature with Geometry and non-metric size
@prefix qudt: <http://qudt.org/schema/qudt/> .
eg:x
a geo:Feature ;
skos:prefLabel "Feature X";
geo:hasGeometry [
geo:asWKT "MULTIPOLYGON (((149.06016 -35.23610, 149.06062 -35.23604, ... , 149.06016 -35.23610)))"^^geo:wktLiteral ;
] ;
geo:hasArea [
qudt:numericValue "2.2E5"^^xsd:double ;
qudt:unit <http://qudt.org/vocab/unit/AC> ; # international acre
] ;
.Here a geo:Feature is described as per the previous example but its area is expressed in non-metric units: the acre.
C.1.1.2.5 Feature with two different Geometry instances indicated
eg:x
a geo:Feature ;
skos:prefLabel "Feature X";
geo:hasGeometry [
rdfs:label "Official boundary" ;
rdfs:comment "Official boundary from the Department of Xxx" ;
geo:asWKT "MULTIPOLYGON (((149.06016 -35.23610, 149.06062 -35.23604, ... , 149.06016 -35.23610)))"^^geo:wktLiteral ;
] ,
[
rdfs:label "Unofficial boundary" ;
rdfs:comment "Unofficial boundary as actually used by everyone" ;
geo:asWKT "MULTIPOLYGON (((149.06016 -35.23610, 149.06062 -35.23604, ... , 149.06016 -35.23610)))"^^geo:wktLiteral ;
] ;
.In this example, Feature X has two different Geometry instances indicated with their difference explained in annotation properties. No GeoSPARQL ontology properties are used to indicate a difference in these Geometry instances thus machine use of this Feature woud not be easily able to differentiate them.
C.1.1.2.6 Feature with two different Geometry instances with different property values
eg:x
a geo:Feature ;
skos:prefLabel "Feature X";
geo:hasGeometry [
geo:hasMetricSpatialResolution "100"^^xsd:double ;
geo:asWKT "MULTIPOLYGON (((149.0601 -35.2361, 149.0606 -35.2360, ... , 149.0601 -35.2361)))"^^geo:wktLiteral ;
] ,
[
geo:hasMetricSpatialResolution "5"^^xsd:double ;
geo:asWKT "MULTIPOLYGON (((149.06016 -35.23610, 149.06062 -35.23604, ... , 149.06016 -35.23610)))"^^geo:wktLiteral ;
] ;
.In this example, Feature X has two different Geometry instances indicated with different spatial resolutions.
Machine use of this Feature would be able to differentiate the two Geometry instances based on this use of geo:hasMetricSpatialResolution.
C.1.1.2.7 Feature with non-metric size
@prefix dbp: <http://dbpedia.org/resource/> .
@prefix qudt: <http://qudt.org/schema/qudt/> .
ex:Seleucia_Artemita
a geo:Feature ;
skos:prefLabel "The route from Seleucia to Artemita"@en ;
geo:hasLength [
qudt:unit ex:Schoenus ;
qudt:value "15"^^xsd:integer ;
]
.
ex:Schoenus
a qudt:Unit;
skos:exactMatch dbp:Schoenus;
.In this example it is not possible to convert the length of the feature to meters, because the historical length unit does not have a known precise conversion factor.
C.1.1.2.8 Feature with two different types of Geometry instances
eg:x
a geo:Feature ;
skos:prefLabel "Feature X";
geo:hasGeometry [
geo:asWKT "POLYGON ((149.06016 -35.23610, 149.060620 -35.236043, ... , 149.06016 -35.23610))"^^geo:wktLiteral ;
] ;
geo:hasCentroid [
geo:asWKT "POINT (149.06017784 -35.23612321)"^^geo:WktLiteral ;
] ;
.Here a Feature instance has two geometries, one indicated with the general property hasGeometry and a second indicated with the specialized property hasCentroid which suggests the role that the indicated geometry plays. Note that while hasGeometry may indicate any type of Geometry, hasCentroid should only be used to indicate a point geometry. It may be informally inferred that the polygonal geometry is the Feature instance’s boundary.
C.1.1.2.9 Feature with multiple sizes
ex:lake-x
a geo:Feature ;
skos:prefLabel "Lake X" ;
eg:hasFeatureCategory <http://example.com/cat/lake> ;
geo:hasMetricArea "9.26E4"^^xsd:double ;
geo:hasMetricVolume "6E5"^^xsd:double ;
.This example shows a Feature instance with area and volume declared. A categorization of the Feature is given through the use of the eg:hasFeatureCategory dummy property which, along with the Feature’s preferred label, indicate that this Feature is a lake. Having both an area and a volume makes sense for a lake.
C.1.1.3 Geometry
The Geometry class is defined in Section 8.6.1.
C.1.1.3.1 Basic Use
eg:y a geo:Geometry ;
skos:prefLabel "Geometry Y";
.Here a Geometry is declared and given a preferred label.
From GeoSPARQL 1.0 use, the most commonly observed use of a Geometry is in relation to a Feature as per the example in [B 1.1.2.2 A Feature related to a Geometry] and often the Geometry is indirectly declared by the use of hasGeometry on the Feature instance indicating a Blank Node. However, it is entirely possible to declare Geometry instances without any Feature instances. The next basic example declares a Geometry instance with an absolute URI and data.
<https://example.com/geometry/y>
a geo:Geometry ;
skos:prefLabel "Geometry Y";
geo:asWKT "MULTIPOLYGON (((149.06016 -35.23610, 149.060620 -35.236043, ... , 149.06016 -35.23610)))"^^geo:wktLiteral ;
.Here the Geometry instance has data in WKT form and, since no CRS is declared, WGS84 is the assumed, default, CRS.
C.1.1.3.2 A Geometry with multiple serializations
eg:x
a geo:Feature ;
skos:prefLabel "Feature X";
geo:hasGeometry [
geo:asWKT "<http://www.opengis.net/def/crs/EPSG/0/4326> MULTIPOLYGON (((149.06016 -35.23610, 149.060620 -35.236043, ... , 149.06016 -35.23610)))"^^geo:wktLiteral ;
geo:asDGGS "<https://w3id.org/dggs/auspix> CELLLIST ((R1234 R1235 R1236 ... R1256))"^^geo:dggsLiteral ;
] ;
.Here a single Geometry, linked to a Feature instance, is expressed using two different serializations: Well-known Text and the DGGS with the AusPIX DGGS indicated by its IRI.
C.1.1.3.3 Geometry with scalar spatial property
eg:x
a geo:Feature ;
skos:prefLabel "Feature X";
geo:hasGeometry eg:x-geo ;
.
eg:x-geo
a geo:Geometry ;
geo:asWKT "MULTIPOLYGON (((149.06016 -35.23610, 149.060620 -35.236043, ... , 149.06016 -35.23610)))"^^geo:wktLiteral ;
geo:hasMetricArea "8.7E4"^^xsd:double;
.This example shows a Feature, eg:x, with a Geometry, eg:x-geo, which has both a serialization (WKT) indicated with the predicate geo:asWKT and a scalar area indicated with the predicate geo:hasMetricArea. While it is entirely possible that scalar areas can be calculated from polygons, it may be efficient to store a pre-calculated scalar area in addition to the polygon. Perhaps the polygon is large and detailed and a one-time calculation with results stored is efficient for repeated use.
This use of a scalar spatial measurement property with a Geometry, here geo:hasMetricArea, is possible since the domain of such properties is geo:SpatialObject, the superclass of both geo:Feature and geo:Geometry.
C.1.1.4 SpatialObjectCollection
geo:SpatialObjectCollection isn’t really intended to be implemented - it’s essentially an abstract class - therefore no examples of its use are given. See the following two sections for examples of the concrete geo:FeatureCollection & geo:GeometryCollection classes.
C.1.1.5 FeatureCollection
This example shows a FeatureCollection instance containing 3 Feature instances.
ex:fc-x
a geo:FeatureCollection ;
dcterms:title "Feature Collection X" ;
rdfs:member
ex:feature-something ,
ex:feature-other ,
ex:feature-another ;
.All of the GeoSPARQL collection classes are unordered since they are subclasses of the generic rdfs:Container, however implementers should consider that there are many ways to order the members of a FeatureCollection such as the Feature instance labels, their areas, geometries or any other property.
C.1.1.6 GeometryCollection
This example shows a GeometryCollection instance containing 3 Geometry instances.
ex:gc-x
a geo:GeometryCollection ;
dcterms:title "Geometry Collection X" ;
rdfs:member
ex:geometry-shape ,
ex:geometry-othershape ,
ex:geometry-anothershape ;
.As per FeatureCollection, the GeometryCollection itself doesn’t impose any ordering on its member Geometry instances, however there are many ways to order them, based on their own properties.
C.1.1.7 Simple Features classes
Most of the geometry seralizations used in GeoSPARQL define the geometry type - point, polygon etc. within the literal, e.g. WKT can encode POLYGON(()) or 'POINT()', however the Simple Features Vocabulary resource within GeoSPARQL 1.1 contains specialised Geometry RDF classes such as sf:Polygon, sf:PolyhedralSurface and others.
It may be appropriate to use these specialized forms of Geometry in circumstances when geometry type differentiation is required within RDF and not withing specialized literal handling. This is the case when type differentiation must occur within plain SPARQL, not GeoSPARQL.
The following example shows a Feature instance with two Geometry instances where the Simple Features Vocabulary classes are used to indicate the Geometry type:
ex:x
a geo:Feature ;
rdfs:label "Feature X" ;
geo:hasGeometry [
a sf:Point ;
geo:asWKT "POINT(...)" ;
rdfs:comment "A point geometry for Feature X, possibly a centroid though not declared one" ;
] ;
geo:hasGeometry [
a sf:Polygon ;
geo:asWKT "POLYGON((...))" ;
rdfs:comment "A polygon geometry for Feature X" ;
] ;There are several GeoSPARQL properties that suggest they could be used with particular Simple Features Vocabulary geometry types, for instance, geo:hasCentroid indicates is could be used with a sf:Point and geo:hasBoundingBox indicates use with an sf:Envelope.
C.1.2 Properties
C.1.2.1 Spatial Object Properties
See the section C.1.1.1.2 Size Properties above.
C.1.2.2 Feature Properties
This example shows a geo:Feature instance with each of the properties defined in Section 6.4 used, except for the properties
geo:hasMetricSize and geo:hasSize, that are intended to be used through their subproperties and geo:hasMetricPerimeterLength and geo:hasPerimeterLength which are examplified in C.1.1.1.2 Size Properties.
@prefix qudt: <http://qudt.org/schema/qudt/> .
eg:x
a geo:Feature ;
skos:preferredLabel "Feature X" ;
geo:hasGeometry [
geo:asWKT "<http://www.opengis.net/def/crs/EPSG/0/4326> POLYGON ((149.06016 -35.23610, ... , 149.06016 -35.23610)))"^^geo:wktLiteral ;
] ;
geo:hasDefaultGeometry [
geo:asWKT "<http://www.opengis.net/def/crs/EPSG/0/4326> POLYGON ((149.0601 -35.2361, ... , 149.0601 -35.2361)))"^^geo:wktLiteral ;
] ;
geo:hasMetricLength "355"^^xsd:double ;
geo:hasLength [
qudt:numericValue 355 ;
qudt:unit <http://qudt.org/vocab/unit/M> ; # meter
] ;
geo:hasMetricArea "8.7E4"^^xsd:double ;
geo:hasArea [
qudt:numericValue 8.7 ;
qudt:unit <http://qudt.org/vocab/unit/HA> ; # hectare
] ;
geo:hasMetricVolume "624432"^^xsd:double ;
geo:hasVolume [
qudt:numericValue 624432 ;
qudt:unit <http://qudt.org/vocab/unit/M3> ; # cubic meter
] ;
geo:hasCentroid [
geo:asWKT "POINT (149.06017 -35.23612)"^^geo:wktLiteral ;
] ;
geo:hasBoundingBox [
geo:asWKT "<http://www.opengis.net/def/crs/EPSG/0/4326> POLYGON ((149.060 -35.236, ... , 149.060 -35.236)))"^^geo:wktLiteral ;
] ;
geo:hasMetricSpatialResolution "5"^^xsd:double ;
geo:hasSpatialResolution [
qudt:numericValue 5 ;
qudt:unit <http://qudt.org/vocab/unit/M> ; # meter
] ;
.The properties defined for this example’s Feature instance are vaguely aligned in that the values are not real but are not unrealistic either. It is outside the scope of GeoSPARQL to validate Feature instances' property values.
Note that this Feature has a 2D Geometry and yet a property indicating a scalar volume: geo:hasVolume. Used in this way, the scalar property is indicating information that cannot be calculated from other information about the Feature such as its geometry. Perhaps a volume for the feature has been estimated or measured in such a way that a 3D geometry was not created.
C.1.2.3 Geometry Properties
This example shows a Geometry instance, a Blank Node, declared in relation to a Feature instance, with each of the properties defined in Section 8.7 used.
@prefix qudt: <http://qudt.org/schema/qudt/> .
@prefix unit: <http://qudt.org/vocab/unit/> .
eg:x
a geo:Feature ;
geo:hasGeometry [
skos:prefLabel "Geometry Y" ;
geo:dimension 2 ;
geo:coordinateDimension 2 ;
geo:spatialDimension 2 ;
geo:isEmpty false ;
geo:isSimple true ;
geo:hasSerialization "<http://www.opengis.net/def/crs/EPSG/0/4326> POLYGON ((149.060 -35.236, ... , 149.060 -35.236)))"^^geo:wktLiteral ;
geo:hasSpatialAccuracy [
qudt:numericValue "30"^^xsd:float ;
qudt:unit unit:CentiM ; # centimetres
] ;
geo:hasMetricSpatialAccuracy "0.3"^^xsd:double ;
] ;
.In this example, each of the properties defined for a Geometry instance has realistic values. For example, the is empty property is set to false since the Geometry contains information.
C.1.2.4 Geometry Serializations
This section shows a Geometry instance for a Feature instance which is represented in all supported GeoSPARQL serlializations. The geometry values given are real geometry values and approximate Moreton Island in Queensland, Australia.
Note that the concrete DGGS serialization used is for example purposes only as it is not formally defined in GeoSPARQL.
eg:x
a geo:Feature ;
geo:hasGeometry [
geo:asWKT """<http://www.opengis.net/def/crs/EPSG/0/4326>
POLYGON ((
153.3610112 -27.0621757,
153.3658177 -27.1990606,
153.421436 -27.3406573,
153.4269292 -27.3607835,
153.4434087 -27.3315078,
153.4183848 -27.2913403,
153.4189391 -27.2039578,
153.4673476 -27.0267166,
153.3610112 -27.0621757
))"""^^geo:wktLiteral ;
geo:asGML """<gml:Polygon
srsName="http://www.opengis.net/def/crs/EPSG/0/4326">
<gml:exterior>
<gml:LinearRing>
<gml:posList>
-27.0621757 153.3610112
-27.1990606 153.3658177
-27.3406573 153.421436
-27.3607835 153.4269292
-27.3315078 153.4434087
-27.2913403 153.4183848
-27.2039578 153.4189391
-27.0267166 153.4673476
-27.0621757 153.3610112
</gml:posList>
</gml:LinearRing>
</gml:exterior>
</gml:Polygon>"""^^go:gmlLiteral ;
geo:asKML """<Polygon>
<outerBoundaryIs>
<LinearRing>
<coordinates>
153.3610112,-27.0621757
153.3658177,-27.1990606
153.421436,-27.3406573
153.4269292,-27.3607835
153.4434087,-27.3315078
153.4183848,-27.2913403
153.4189391,-27.2039578
153.4673476,-27.0267166
153.3610112,-27.0621757
</coordinates>
</LinearRing>
</outerBoundaryIs>
</Polygon>"""^^go:kmlLiteral ;
geo:asGeoJSON """{
"type": "Polygon",
"coordinates": [[
[153.3610112, -27.0621757],
[153.3658177, -27.1990606],
[153.421436, -27.3406573],
[153.4269292, -27.3607835],
[153.4434087, -27.3315078],
[153.4183848, -27.2913403],
[153.4189391, -27.2039578],
[153.4673476, -27.0267166],
[153.3610112, -27.0621757]
]]
}"""^^geo:geoJSONLiteral ;
geo:asDGGS """<https://w3id.org/dggs/auspix> CELLLIST ((R8346031 R8346034 R8346037
R83460058 R83460065 R83460068 R83460072 R83460073 R83460074 R83460075 R83460076
R83460077 R83460078 R83460080 R83460081 R83460082 R83460083 R83460084 R83460085
R83460086 R83460087 R83460088 R83460302 R83460305 R83460308 R83460320 R83460321
R83460323 R83460324 R83460326 R83460327 R83460332 R83460335 R83460338 R83460350
R83460353 R83460356 R83460362 R83460365 R83460380 R83460610 R83460611 R83460612
R83460613 R83460614 R83460615 R83460617 R83460618 R83460641 R83460642 R83460644
R83460645 R83460648 R83460672 R83460686 R83463020 R83463021 R834600487 R834600488
R834600557 R834600558 R834600564 R834600565 R834600566 R834600567 R834600568
R834600571 R834600572 R834600573 R834600574 R834600575 R834600576 R834600577
R834600578 R834600628 R834600705 R834600706 R834600707 R834600708 R834600712
R834600713 R834600714 R834600715 R834600716 R834600717 R834600718 R834601334
R834601335 R834601336 R834601337 R834601338 R834601360 R834601361 R834601363
R834601364 R834601366 R834601367 R834601600 R834601601 R834601603 R834601606
R834601630 R834601633 R834603220 R834603221 R834603223 R834603224 R834603226
R834603227 R834603250 R834603251 R834603253 R834603256 R834603280 R834603283
R834603510 R834603511 R834603512 R834603513 R834603514 R834603515 R834603516
R834603517 R834603540 R834603541 R834603543 R834603544 R834603546 R834603547
R834603570 R834603573 R834603576 R834603681 R834603682 R834603684 R834603685
R834603687 R834603688 R834603810 R834603830 R834603831 R834603832 R834603833
R834603834 R834603835 R834603836 R834603837 R834603860 R834603861 R834603863
R834603864 R834603866 R834603867 R834606021 R834606022 R834606024 R834606025
R834606028 R834606052 R834606055 R834606160 R834606161 R834606162 R834606164
R834606165 R834606167 R834606168 R834606200 R834606203 R834606206 R834606230
R834606233 R834606236 R834606260 R834606263 R834606266 R834606401 R834606402
R834606405 R834606408 R834606432 R834606471 R834606472 R834606474 R834606475
R834606477 R834606478 R834606500 R834606503 R834606506 R834606530 R834606533
R834606536 R834606560 R834606563 R834606566 R834606712 R834606715 R834606718
R834606750 R834606751 R834606752 R834606753 R834606754 R834606755 R834606757
R834606758 R834606781 R834606782 R834606784 R834606785 R834606788 R834606800
R834606803 R834606806 R834606807 R834606830 R834606831 R834606833 R834606834
R834606835 R834606836 R834606837 R834606838 R834606870 R834606873 R834606874
R834606876 R834606877 R834630122 R834630125 R834630226 R834630230 R834630231
R834630232 R834630234 R834630235 R834630237 R834630238 R834630240 R834630241
R834630242 R834630243 R834630244 R834630245 R834630246 R834630247 R834630261
R834630262 R834630264 R834630265 R834630268 R834630270 R834630271 R834630273
R834630276 R834630502))"""^^geo:dggsLiteral ;
] ;
.C.2 Example SPARQL Queries & Rules
This Section provides example data and then illustrates the use of GeoSPARQL functions and the application of rules with that data.
C.2.1 Example Data
The following RDF data (Turtle format) encodes application-specific spatial data. The resulting spatial data is illustrated in the figure below. The RDF statements define the feature class my:PlaceOfInterest, and two properties are created for associating geometries with features: my:hasExactGeometry and my:hasPointGeometry. my:hasExactGeometry is designated as the default geometry for the my:PlaceOfInterest feature class.
All the following examples use the parameter values relation_family = Simple Features, serialization = WKT, and version = 1.0.
@prefix geo: <http://www.opengis.net/ont/geosparql#> .
@prefix my: <http://example.org/ApplicationSchema#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix sf: <http://www.opengis.net/ont/sf#> .
my:PlaceOfInterest a rdfs:Class ;
rdfs:subClassOf geo:Feature .
my:A a my:PlaceOfInterest ;
my:hasExactGeometry my:AExactGeom ;
my:hasPointGeometry my:APointGeom .
my:B a my:PlaceOfInterest ;
my:hasExactGeometry my:BExactGeom ;
my:hasPointGeometry my:BPointGeom .
my:C a my:PlaceOfInterest ;
my:hasExactGeometry my:CExactGeom ;
my:hasPointGeometry my:CPointGeom .
my:D a my:PlaceOfInterest ;
my:hasExactGeometry my:DExactGeom ;
my:hasPointGeometry my:DPointGeom .
my:E a my:PlaceOfInterest ;
my:hasExactGeometry my:EExactGeom .
my:F a my:PlaceOfInterest ;
my:hasExactGeometry my:FExactGeom .
my:hasExactGeometry a rdf:Property ;
rdfs:subPropertyOf geo:hasDefaultGeometry,
geo:hasGeometry .
my:hasPointGeometry a rdf:Property ;
rdfs:subPropertyOf geo:hasGeometry .
my:AExactGeom a sf:Polygon ;
geo:asWKT """<http://www.opengis.net/def/crs/OGC/1.3/CRS84>
Polygon((-83.6 34.1, -83.2 34.1, -83.2 34.5,
-83.6 34.5, -83.6 34.1))"""^^geo:wktLiteral.
my:APointGeom a sf:Point ;
geo:asWKT """<http://www.opengis.net/def/crs/OGC/1.3/CRS84>
Point(-83.4 34.3)"""^^geo:wktLiteral.
my:BExactGeom a sf:Polygon ;
geo:asWKT """<http://www.opengis.net/def/crs/OGC/1.3/CRS84>
Polygon((-83.6 34.1, -83.4 34.1, -83.4 34.3,
-83.6 34.3, -83.6 34.1))"""^^geo:wktLiteral.
my:BPointGeom a sf:Point ;
geo:asWKT """<http://www.opengis.net/def/crs/OGC/1.3/CRS84>
Point(-83.5 34.2)"""^^geo:wktLiteral.
my:CExactGeom a sf:Polygon ;
geo:asWKT """<http://www.opengis.net/def/crs/OGC/1.3/CRS84>
Polygon((-83.2 34.3, -83.0 34.3, -83.0 34.5,
-83.2 34.5, -83.2 34.3))"""^^geo:wktLiteral.
my:CPointGeom a sf:Point ;
geo:asWKT """<http://www.opengis.net/def/crs/OGC/1.3/CRS84>
Point(-83.1 34.4)"""^^geo:wktLiteral.
my:DExactGeom a sf:Polygon ;
geo:asWKT """<http://www.opengis.net/def/crs/OGC/1.3/CRS84>
Polygon((-83.3 34.0, -83.1 34.0, -83.1 34.2,
-83.3 34.2, -83.3 34.0))"""^^geo:wktLiteral.
my:DPointGeom a sf:Point ;
geo:asWKT """<http://www.opengis.net/def/crs/OGC/1.3/CRS84>
Point(-83.2 34.1)"""^^geo:wktLiteral.
my:EExactGeom a sf:LineString ;
geo:asWKT """<http://www.opengis.net/def/crs/OGC/1.3/CRS84>
LineString(-83.4 34.0, -83.3 34.3)"""^^geo:wktLiteral.
my:FExactGeom a sf:Point ;
geo:asWKT """<http://www.opengis.net/def/crs/OGC/1.3/CRS84>
Point(-83.4 34.4)"""^^geo:wktLiteral.C.2.2 Example Queries
This Section illustrates the use of GeoSPARQL functions through a series of example queries.
C.2.2.1
Find all features that feature my:A contains, where spatial calculations are based on my:hasExactGeometry.
PREFIX my: <http://example.org/ApplicationSchema#>
PREFIX geo: <http://www.opengis.net/ont/geosparql#>
PREFIX geof: <http://www.opengis.net/def/function/geosparql/>
SELECT ?f
WHERE {
my:A my:hasExactGeometry ?aGeom .
?aGeom geo:asWKT ?aWKT .
?f my:hasExactGeometry ?fGeom .
?fGeom geo:asWKT ?fWKT .
FILTER (
geof:sfContains(?aWKT, ?fWKT) &&
!sameTerm(?aGeom, ?fGeom)
)
)Result:
| ?f |
|---|
|
|
C.2.2.2
Find all features that are within a transient bounding box geometry, where spatial calculations are based on my:hasPointGeometry.
PREFIX my: <http://example.org/ApplicationSchema#>
PREFIX geo: <http://www.opengis.net/ont/geosparql#>
PREFIX geof: <http://www.opengis.net/def/function/geosparql/>
SELECT ?f
WHERE {
?f my:hasPointGeometry ?fGeom .
?fGeom geo:asWKT ?fWKT .
FILTER (
geof:sfWithin(
?fWKT,
"<http://www.opengis.net/def/crs/OGC/1.3/CRS84>
Polygon ((-83.4 34.0, -83.1 34.0,
-83.1 34.2, -83.4 34.2,
-83.4 34.0))"^^geo:wktLiteral
)
)
}Result:
| ?f |
|---|
|
C.2.2.3
Find all features that touch the union of feature my:A and feature my:D, where computations are based on my:hasExactGeometry.
PREFIX my: <http://example.org/ApplicationSchema#>
PREFIX geo: <http://www.opengis.net/ont/geosparql#>
PREFIX geof: <http://www.opengis.net/def/function/geosparql/>
SELECT ?f
WHERE {
?f my:hasExactGeometry ?fGeom .
?fGeom geo:asWKT ?fWKT .
my:A my:hasExactGeometry ?aGeom .
?aGeom geo:asWKT ?aWKT .
my:D my:hasExactGeometry ?dGeom .
?dGeom geo:asWKT ?dWKT .
FILTER (
geof:sfTouches(
?fWKT,
geof:union(?aWKT, ?dWKT)
)
)
}Result:
| ?f |
|---|
|
C.2.2.4
Find the 3 closest features to feature my:C, where computations are based on my:hasExactGeometry.
PREFIX uom: <http://www.opengis.net/def/uom/OGC/1.0/>
PREFIX my: <http://example.org/ApplicationSchema#>
PREFIX geo: <http://www.opengis.net/ont/geosparql#>
PREFIX geof: <http://www.opengis.net/def/geosparql/function>
SELECT ?f
WHERE {
my:C my:hasExactGeometry ?cGeom .
?cGeom geo:asWKT ?cWKT .
?f my:hasExactGeometry ?fGeom .
?fGeom geo:asWKT ?fWKT .
FILTER (?fGeom != ?cGeom)
}
ORDER BY ASC (geof:distance(?cWKT, ?fWKT, uom:metre))
LIMIT 3Result:
| ?f |
|---|
|
|
|
C.2.2.5
Find the maximum and minimum coordinates of a given set of geometries.
PREFIX geo: <http://www.opengis.net/ont/geosparql#>
PREFIX geof: <http://www.opengis.net/def/function/geosparql/>
SELECT ?minX ?minY ?minZ ?maxX ?maxY ?maxZ
WHERE {
BIND ("<http://www.opengis.net/def/crs/OGC/1.3/CRS84>
Polygon Z((-83.4 34.0 0, -83.1 34.0 1,
-83.1 34.2 1, -83.4 34.2 1,
-83.4 34.0 0))"^^geo:wktLiteral) AS ?testgeom)
BIND(geof:minX(?testgeom) AS ?minX)
BIND(geof:maxX(?testgeom) AS ?maxX)
BIND(geof:minY(?testgeom) AS ?minY)
BIND(geof:maxY(?testgeom) AS ?maxY)
BIND(geof:maxZ(?testgeom) AS ?maxZ)
BIND(geof:minZ(?testgeom) AS ?minZ)
}Result:
| ?minX | ?minY | ?minZ | ?maxX | ?maxY | ?maxZ |
|---|---|---|---|---|---|
|
|
|
|
|
|
C.2.3 Example Rule Application
This section illustrates the query transformation strategy for implementing GeoSPARQL rules.
C.2.3.1
Find all features or geometries that overlap feature my:A.
Original Query:
PREFIX geo: <http://www.opengis.net/ont/geosparql#>
SELECT ?f
WHERE { ?f geo:sfOverlaps my:A }Transformed Query (application of transformation rule geor:sfOverlaps):
PREFIX my: <http://example.org/ApplicationSchema#>
PREFIX geo: <http://www.opengis.net/ont/geosparql#>
PREFIX geof: <http://www.opengis.net/def/function/geosparql/>
SELECT ?f
WHERE {
{ # check for asserted statement
?f geo:sfOverlaps my:A }
UNION
{ # feature – feature
?f geo:hasDefaultGeometry ?fGeom .
?fGeom geo:asWKT ?fSerial .
my:A geo:hasDefaultGeometry ?aGeom .
?aGeom geo:asWKT ?aSerial .
FILTER (geof:sfOverlaps(?fSerial, ?aSerial))
}
UNION
{ # feature – geometry
?f geo:hasDefaultGeometry ?fGeom .
?fGeom geo:asWKT ?fSerial .
my:A geo:asWKT ?aSerial .
FILTER (geof:sfOverlaps(?fSerial, ?aSerial))
}
UNION
{ # geometry – feature
?f geo:asWKT ?fSerial .
my:A geo:hasDefaultGeometry ?aGeom .
?aGeom geo:asWKT ?aSerial .
FILTER (geof:sfOverlaps(?fSerial, ?aSerial))
}
UNION
{ # geometry – geometry
?f geo:asWKT ?fSerial .
my:A geo:asWKT ?aSerial .
FILTER (geof:sfOverlaps(?fSerial, ?aSerial))
}Result:
| ?f |
|---|
|
|
|
|
C.2.4 Example Geometry Serialization Conversion Functions
For the geometry literal values in C.1.2.4 Geometry Serializations:
Application of the function geof:asWKT to the GML, KML, GeoJSON and DGGS literals should return WKT literal and similarly for each of the other conversion methods, geof:asGML, geof:asKML, geof:asGeoJSON & geof:asDGGS.
Annex D - Usage of SHACL shapes (informative)
D.0 Overview
This Annex provides guidance on the usage of the SHACL shapes included with GeoSPARQL 1.1.
The Shapes Constraint Language SHACL allows the specification of constraints on RDF data, phrased as a set of conditions modeled in "Shape" graphs.
In GeoSPARQL 1.1, SHACL Shapes area defined in such a way that they validate anticipated graph structures expected by Requirements defined in the standard. Users may validate a given RDF document claiming conformance to GeoSPARQL 1.1 by using these Shapes and use the validation results to correct any mistakes.
D.1 Tools
SHACL Shapes provided with GeoSPARQL are used to verify the graph structure of GeoSPARQL graphs. There are several SHACL tools that one can using to validate data using this Shapes information:
-
PySHACL: A Python implementation based on the RDF library RDFlib
-
Apache Jena SHACL: a Java implementation, based on Apache Jena
-
SHACL Playground: An online, JavaScript-based implementation that allows validation without local tools
-
Triple Stores: SHACL validation is part of many triple store implementations:
Validators produce error messages and warnings based on the SHACL standard’s defined reporting structure.
D.2 Scope of SHACL Shapes provided with GeoSPARQL
The SHACL Shapes defined in the GeoSPARQL 1.1 standard all target the verification of specific graph structures, but only in very few cases validate the content of literal types. In particular, the following attributes of the graph are validated:
-
Proper usage of GeoSPARQL classes: These Shapes check for a proper usage of instances of GeoSPARQL classes. For example, we check that instances of collection classes should at least have one element and that instances of Geometry classes should at least have one serilization to avoid creating graphs which contain nodes without necessary information.
-
Geometry property consistency: Certain checks are applied for properties describing geometries. For example we check dimensionality properties for corresponding values.
-
Rudimentary checks of literal contents: The SHACL Shapes defined in this standard do not substitute a verification of literal contents by validators of the respective data formats. However, they define checks using regular expressions to detect a falsely formatted geospatial literal. For example, if a GeoJSON literal is declared using its literal type, a SHACL shape will check for curly brackets to be present (as they are part of the JSON specification).
D.3 Table of SHACL Shapes
| SHACL Shape ID | Severity | Test purpose | Requirements tested |
|---|---|---|---|
Violation |
Each node with an incoming geo:hasGeometry, or a specialization of it, should have at minimum one outgoing relation that is either geo:hasSerialization, or a specialization of it. |
[req_geometry-extension_feature_properties], [req_geometry-extension_geometry_properties] |
|
Violation |
Each node with an incoming geo:hasGeometry, or a specialization of it, can have a maximum of one outgoing geo:asWKT relation. |
[req_geometry-extension_geometry_properties] [req_geometry-extension_geometry-as-wkt-literal] |
|
Violation |
Each node with an incoming geo:hasGeometry, or a specialization of it, can have a maximum of one outgoing geo:asGML relation. |
[req_geometry-extension_geometry_properties] [req_geometry-extension_geometry-as-gml-literal] |
|
Violation |
Each node with an incoming geo:hasGeometry, or a specialization of it, can have a maximum of one outgoing geo:asGeoJSON relation. |
[req_geometry-extension_geometry_properties] [req_geometry-extension_geometry-as-geojson-literal] |
|
Violation |
Each node with an incoming geo:hasGeometry, or a specialization of it, can have a maximum of one outgoing geo:asKML relation. |
[req_geometry-extension_geometry_properties] [req_geometry-extension_geometry-as-kml-literal] |
|
Violation |
Each node with one or more outgoing relations that are either geo:hasSerialization, or a specialization of it, should have at least one incoming geo:hasGeometry relation or a specialization of it. |
||
Violation |
A node that has an incoming geo:hasGeometry property, or specialization of it, cannot have an outgoing geo:hasGeometry property, or a specialization of, it at the same time (a geo:Feature cannot be a geo:Geometry at the same time) |
||
Violation |
The target of a geo:hasSerialization property, or a specialization of, it should be an RDF literal |
||
Violation |
The target of a geo:asWKT property should be an RDF literal with datatype geo:wktLiteral |
||
Violation |
The target of a geo:asGML property should be an RDF literal with datatype geo:gmlLiteral |
||
Violation |
The target of a geo:asGeoJSON property should be an RDF literal with datatype geo:geoJSONLiteral |
||
Violation |
The target of a geo:asKML property should be an RDF literal with datatype geo:kmlLiteral |
||
Violation |
A geo:Geometry node should have a maximum of one outgoing geo:coordinateDimension property |
||
Violation |
A geo:Geometry node should have a maximum of one outgoing geo:dimension property |
||
Violation |
A geo:Geometry node should have a maximum of one outgoing geo:isEmpty property |
||
Violation |
A geo:Geometry node should have a maximum one outgoing geo:isSimple property |
||
Violation |
A geo:Geometry node should have maximum of one outgoing geo:spatialDimension property |
||
Violation |
A geo:Geometry node should have maximum of one outgoing geo:hasSpatialResolution property |
||
Violation |
A geo:Geometry node should have maximum of one outgoing geo:hasSpatialAccuracy property |
||
Violation |
A geo:Geometry node should have maximum of one outgoing geo:hasMetricSpatialAccuracy property |
||
Violation |
A geo:Geometry node should have maximum of one outgoing geo:hasMetricSpatialResolution property |
||
Violation |
The content of an RDF literal with an incoming geo:asWKT relation must conform to a well-formed WKT string, as defined by its official specification (Simple Features Access) |
||
Violation |
The content of an RDF literal with an incoming geo:asWKT relation must conform to a well-formed WKT string, as defined by its official specification (Simple Features Access) |
||
Violation |
The content of an RDF literal with an incoming geo:asGeoJSON relation must conform to a well-formed GeoJSON geometry string, as defined by its official specification |
||
Violation |
The content of an RDF literal with an incoming geo:asKML relation must conform to a well-formed KML geometry XML string, as defined by its official specification |
||
Violation |
If both geo:dimension and geo:coordinateDimension properties are asserted, the value of geo:dimension should be less than or equal to the value of geo:coordinateDimension |
||
Violation |
An instance of geo:FeatureCollection should have at least one outgoing rdfs:member relation |
||
Violation |
An instance of geo:FeatureCollection should only have outgoing rdfs:member going to geo:Feature instances |
||
Violation |
An instance of geo:GeometryCollection should have at least one outgoing rdfs:member relation |
||
Violation |
An instance of geo:GeometryCollection should only have outgoing rdfs:member relations to geo:Geometry instances |
||
Violation |
An instance of geo:SpatialObjectCollection should have at least one outgoing rdfs:member relation |
||
Violation |
An instance of geo:SpatialObjectCollection should only have outgoing rdfs:member relations going to geo:SpatialObject instances, or subclasses of them |
Annex E - Alignments (informative)
E.0 Overview
This Annex provides alignments of GeoSPARQL to other well known ontologies that are either commonly used with GeoSPARQL or could be.
The prefixes used for the ontologies mapped to in all following sections are given in the following table.
as: |
|
dcterms: |
|
geo: |
|
geom: |
|
gn: |
|
juso: |
|
lgd: |
|
locn: |
|
obo: |
|
osm: |
|
osmm: |
|
osmt: |
|
pos: |
|
prov: |
|
rdf: |
|
rdfs: |
|
sdo: |
|
sosa: |
|
spatialuk: |
|
spatialukgeom: |
|
spatial: |
|
ssn: |
|
time: |
|
wdt: |
E.1 ISA Programme Location Core Vocabulary (LOCN)
LOCN Source: https://www.w3.org/ns/locn
The LOCN specification provides notes on the use of GeoSPARQL literals (see https://www.w3.org/ns/locn#changes).
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
LOCN states that |
|||
Although LOCN does not explicitly indicate spatial or geometry properties for |
|||
In LOCN, class |
|||
In LOCN, the usage note to property |
E.2 WGS84 Geo Positioning: an RDF vocabulary (POS)
POS Source: http://www.w3.org/2003/01/geo/
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
Both classes are unrestricted, essentially abstract classes |
|||
Via |
|||
A special datatype is not indicated for use with this property by POS, unlike GeoSPARQL’s |
|||
E.3 W3C Activity Streams Vocabulary
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
AS places are only defined for point geometries |
|||
AS expresses the accuracy in percent |
|||
The altitude property can be expressed as a Z coordinate in GeoSPARQL-compatible literals |
|||
AS defines the range of this property as xsd:float |
|||
AS defines the range of this property as xsd:float |
E.4 Geonames Ontology (GN)
Geonames source: http://www.geonames.org/ontology/documentation.html
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
The GN class is defined as "A feature described in geonames database…" |
|||
The GN class' definition reads "A class of features" |
|||
A |
|||
E.5 NeoGeo Vocabulary
NeoGeo Source: http://geovocab.org/ / http://geovocab.org/doc/neogeo/
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
Sub proerty not equivalent property since the NeoGeo property has more restrictive domain & range |
|||
GeoSPARQL doesn’t have a BoundingBox class but has a generic Geometry class that is the range of the |
|||
|
|
-
The
geom:bboxproperty relates a Geometry to another Geometry and is thus not equivalent to GeoSPARQL’s Feature-to-Geometrygeo:hasBoundingBox.-
An equivalent to
geo:bboxcould be made using ageo:Featurewith ageo:Geometry, indicated bygeo:hasGeometryand a second, specialised Bounding Boxgeo:Geometryindicated withgeo:hasBoundingBox
-
E.6 Juso Ontology
Juso Source: http://rdfs.co/juso/
Juso contains mappings to GeoSPARQL but uses owl:sameAs which it should instead use owl:equivalentClass.
| From Element | Mapping relation | To Element |
|---|---|---|
E.7 Time Ontology in OWL (TIME)
TIME Source: https://www.w3.org/TR/owl-time/
There are no direct class or property correspondences between GeoSPARQL and TIME however class patterning is similar:
-
TIME uses
time:hasTimeto indicate that something has a temporal projection -
GeoSPARQL uses
geo:hasGeometryto indicate that ageo:Featurehas a spatial projection
and
-
TIME uses properties such as
time:inXSDDateto indicate the position of temporal entities on a temporal reference system -
GeoSPARQL uses properties such as
geo:asWKTto indicate the position of spatial entities (Geometries) on spatial reference systems
OWL TIME sets no domain for time:hasTime thus this property may be used with anything, including a GeoSPARQL geo:Feature so that a spatio-temporal Feature may be indicated like this:
:flooded-area-x
a geo:Feature ;
geo:hasGeometry [
a geo:Geometry ;
geo:asWKT "POLYGON (((...)))"^^geo:wktLiteral ;
] ;
time:hasTime [
a time:ProperInterval ;
time:hasBeginning [
time:inXSDDate "..."^^xsd:date ;
] ;
time:hasEnd [
time:inXSDDate "..."^^xsd:date ;
] ;
] ;
.In the above example, :flooded-area-x is a spatio-temporal Feature that has both a GeoSPARQL spatial projection - a geo:Geometry - and a temporal projection - a time:ProperInterval which is a specialized form of time:TemporalEntity.
Another possible use of TIME with GeoSPARQL is to assign temporality to individual geo:Geometry instances. This is allowed given time:hasTime's open domain:
:flooded-area-x
a geo:Feature ;
geo:hasGeometry [
a geo:Geometry ;
geo:asWKT "POLYGON (((...)))"^^geo:wktLiteral ;
time:hasTime [ ... ] ;
] ;
.In contrast to the first example, :flooded-area-x is inferred to be a spatio-temporal Feature but since it is the Geometry of :flooded-area-x that has a temporality, it is possible to describe other Geometries of :flooded-area-x with other temporalities.
E.8 schema.org
schema.org Source: https://schema.org
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
A GeoShape can various literal geometry representation |
|||
Since |
|||
GoCoordinates uses direct lat, long, elevation etc properties to indicate position, not a while geometry serialization but it is nevertheless a form of a Geometry |
|||
E.9 Semantic Sensor Network Ontology (SSN)
SSN Source: https://www.w3.org/TR/vocab-ssn/
SSN and GeoSPARQL do not cover overlapping concerns directly and therefore there are no direct class or property correspondences between them, however SSN provides advice on the use of GeoSPARQL for location, see Section 7.1 (https://www.w3.org/TR/vocab-ssn/#x7-1-location):
GeoSPARQL … provides a flexible and relatively complete platform for geospatial objects, that fosters interoperability between geo-datasets. To do so, these entities can be declared as instances of
geo:Featureand geometries can be assigned to them via the geo:hasGeometry property. In case of classes, e.g., specific features of interests such as rivers, these can be defined as subclasses ofgeo:Feature.
E.10 DCMI Metadata Terms (DCTERMS)
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
A Location is a "A spatial region or named place." |
|||
|
-
dcterms:spatial: "Spatial characteristics of the resource". The range of this property includes adcterms:Location, so it is a property for indicating ageo:Feature, for which GeoSPARQL has no equivalent, but perhaps also for indicating ageo:Geometry, thus the subPropertyOf mapping above. -
dcterms:coverage: "The spatial or temporal topic of the resource, spatial applicability of the resource, or jurisdiction under which the resource is relevant". This is a more generic form ofdcterms:spatialbut, since there is no direct GeoSPARQL mapping fordcterms:spatial, there is no direct mapping for this property either.
DCTERMS-related geometry literals, such as the DCMI Box Encoding Scheme [14] and the DCMI Point Encoding Scheme [15]
could be indicated as GeoSPARQL geometry literals if a literal datatype were created for each. For example, the DCMI Point Encoding Scheme example of "The highest point in Australia" with the literal value
east=148.26218; north=-36.45746; elevation=2228; name=Mt. Kosciusko might be encoded in GeoSPARQL like this:
:mt-kosciusko
a geo:Feature ;
geo:hasGeometry [
a geo:Geometry ;
geo:hasSerialization "east=148.26218; north=-36.45746; elevation=2228; name=Mt. Kosciusko"^^ex:dcmiPoint ;
] ;
.E.11 The Provenance Ontology (PROV)
PROV Source: https://www.w3.org/TR/prov-o/
From GeoSPARQL’s point of view, PROV is an "upper" ontology - one dealing with more abstract concepts - and only one of PROV’s three main classes of object - Entity, Activity & Agent - has direct relations to GeoSPARQL classes and that is Entity. This is because GeoSPARQL characterizes things - spatial objects - which are a kind of Entity but does not deal with events (Activity) or things with agency (Agent).
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
|
PROV’s class is a generic collection class and GeoSPARQL’s property is clearly a specialized form of it that may only consist of certain class instances ( |
||
All SpatialObjects fit within PROV’s Entity’s definition: "An entity is a physical, digital, conceptual, or other kind of thing with some fixed aspects; entities may be real or imaginary." |
|||
A Location "…can be an identifiable geographic place (ISO 19112), but it can also be a non-geographic place such as a directory, row, or column" so seem to be wider in scope than GeoSPARQL’s Feature although a Feature could indeed be something such as a "directory, row, or column" |
-
The PROV property
prov:atLocationindicatesprov:Locationinstances, which may begeo:Featureinstances, but GeoSPARQL has no property to indicate ageo:Feature, so no mapping is possible. Indicating features is commonly done in ontologies which use GeoSPARQL but not within GeoSPARQL. -
Derivative relations between GeoSPARQL objects could be modelled using PROV, for instance a BoundingBox may be indicated as having been derived from a Polygon like this:
:bounding-box-y prov:wasDerivedFrom :polygon-x .
E.12 WikiData
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
The Wikidata description of this property labeled "coordinate location" note that "For Earth, please note that only WGS84 coordinating system is supported at the moment" but that is a system limit, not an ontological one |
|||
This Wikidata property labeled "geoshape" indicated GeoJSON geometry literal content for a Feature, but it allows information other than just Geometry in the GeoJSON whereas GeoSPARQL does not. |
|||
This Wikidata property labeled "KML File" links to a KML file which is related to the respective instance. This may not be the same representation as in GeoSPARQL, as GeoSPARQL KML literals only encode the geometry part of a KML. |
|||
The Wikidata class is labeled "geographic region" and thus is a subclass of the more general |
|||
The Wikidata class is labeled "geographical feature" and thus corresponds to |
|||
The Wikidata class is labeled "spatial object" and thus corresponds to |
|||
The Wikidata property is labeled "contains administrative territorial entity" but also alternatively labeled "contains", "has districts" and others. There are likely many other specialized forms of |
|||
The Wikidata property is labeled "part of" and is sometimes used to indicate Feature parthood. There are likely other parthood properties like this in Wikipedia that may also be used as superproperties of GeoSPARQL feature relations properties. The Wikidata inverse is |
|||
The property labeled "has part" is the inverse of |
|||
The Wikidata property is labeled "located in the administrative territorial entity" and is essentially the inverse of |
|||
The Wikidata property is labeled "located in/on physical feature" and is indicated for use with a "(geo)physical feature" and not to be used for administrative features where |
|||
The Wikidata class is labeled "geomorphological unit" and is one of many Wikidata feature classes that could be expressed as a subclass of |
|||
The Wikidata property is labeled "area". It indicates a microformat - NUMBER + SPACE + ALLOWED_UNIT_LABEL - with a fixed set of ALLOWED_UNIT_LABELs to present values and units of measure. |
E.13 OpenStreetMap Ontologies
There are several approaches to make OpenStreetMap data accessible in the Linked Open Data cloud.
E.13.1 LinkedGeoData
LinkedGeoData emerged from a research project connecting OpenStreetMap representations to an ontology model.
In this model, specific values of OpenStreetMap tags, e.g. the values of amenity tags are converted to owl:Class representations using an automated process.
Every class defined in this way represented a geo:Feature and is linked to either a Geometry or a latitude longitude representation.
Hence, every linked geodata class can be considered a geo:Feature in the sense of GeoSPARQL.
From Element |
Mapping relation |
To Element |
Notes |
Any LGD Class |
Any class defined in the LinkedGeoData ontology is a subclass of |
E.13.2 OpenStreetMap RDF (Sophox)
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
The OpenStreetMap RDF property osmm:loc includes WKTliterals which depending on the type of the subject instance describe an OSM node or the centroid of a way or OSM relation |
|||
|
The OpenStreetMap RDF property |
||
|
The OpenStreetMap RDF property |
||
|
The OpenStreetMap RDF property |
||
The OpenStreetMap RDF property osmm:has describes that a relation contains a way or that a way contains a node |
|||
|
The OpenStreetMap RDF property |
||
|
The OpenStreetMap RDF property |
E.13.3 Routable Tiles Ontology
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
|
The class osm:Element is equivalent to a |
||
|
The class osm:Node is equivalent to a |
||
|
The class osm:Way is equivalent to a |
||
|
The class osm:Relation is equivalent to a |
E.14 Ordnance Survey UK Spatial Ontology
http://www.ordnancesurvey.co.uk/legacy/ontologies/spatialrelations.owl & http://www.ordnancesurvey.co.uk/legacy/ontologies/geometry.owl
|
Note
|
These two ontologies will be withdrawn during 2022. |
The ontology authors note: "We are pleased to have contributed to the discussion some ten years ago but recognize that the subject area has moved on. We would not recommend people starting to relate to our ontology now, and we look forward to migrating to some more authoritative one in due course."
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
- |
Distance in metres east of National Grid origin |
||
- |
Distance in metres north of National Grid origin |
||
The range of spatialukgeom:extent is constrained to 2D geometries |
|||
The properties are equivalent, but the range of `spatialukgeom:asGML is more general: An rdf:XMLLiteral |
-
spatialuk:eastingdescribes a latitude coordinate east of the national UK grid and GeoSPARQL does not contain modelling of individual coordinate reference system elements -
spatialuk:northingdescribes a longitude coordinate north of the national UK grid so, as above, has not GeoSPARQL equivalent
E.15 CIDOC CRM Geo
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
The CIDOC CRMgeo class SP1_PhenomenalSpaceTimeVolume is a subclass of geo:Feature as described in the CRMgeo 1.2 specification document. |
|||
The CIDOC CRMgeo class SP2_PhenomenalPlace is a subclass of |
|||
The CIDOC CRMgeo class SP5_GeometricPlaceExpression is a subclass of |
|||
|
The CIDOC CRMgeo class SP6_DeclarativePlace is a subclass of geo:Geometry as described in the CRMgeo 1.2 specification document. |
||
|
The CIDOC CRMgeo class SP7_DeclarativePlace is a subclass of geo:Geometry as described in the CRMgeo 1.2 specification document. |
||
The CIDOC CRMgeo class SP10_DeclarativeTimeSpan is a subclass of geo:Geometry as described in the CRMgeo 1.2 specification document. |
|||
The CIDOC CRMgeo class SP14_TimeExpression is a subclass of geo:Geometry as described in the CRMgeo 1.2 specification document. |
|||
The CIDOC CRMgeo class SP15_Geometry is a subclass of geo:Geometry as described in the CRMgeo 1.2 specification document. |
E.16 Basic Formal Ontology (BFO)
BFO Source: https://basic-formal-ontology.org/bfo-2020.html, and from there, an OWL ontology of BFO2020 at https://github.com/BFO-ontology/BFO-2020
| From Element | Mapping relation | To Element | Notes |
|---|---|---|---|
|
BFO’s "independent continuant" is the superclass of "material entity" & "immaterial entity" which are mapped to Feature & Geometry respectively, so at least some independent continuants must be Spatial Objects |
||
|
BFO’s "spatial region" class is described as a "spatial projection of a portion of spacetime" so Geometry appears to be a subclass of this as it’s "A coherent set of direct positions in space" |
||
|
BFO’s "information content entity" class is described as "an entity that represents information about some other entity", so Geometry appears to be subclass of this as well as "spatial region" since in GeoSPARQL, Geometry gives the details of the spatial projection of a Feature. |
||
|
A BFO "material entity" is something that "has some portion of matter as continuant part" and some Features are such, however Features may be imaginary too |
||
|
BFO’s sites either cover the same areas as, or have locations determined in relation to, material entities, so sites are Features but not necessarily the other way around |
||
|
The BFO property links a thing that is not a spatial region to a spatial region, so it can be used as |
||
|
A transitive mapping from the mapping above. Temporal qualification can be used with GeoSPARQL, see the OWL TIME alignment. |
||
|
The BFO property "located in at all times" is a super property of |
||
|
A transitive mapping from the mapping above. Temporal qualification can be used with GeoSPARQL, see the OWL TIME alignment. |
||
|
The BFO property relates a temporal activity to a spatial region but since GeoSPARQL has no notion of events, no mapping to this property can be made. However, BFO indicates this property should be used with a BFO "spatial region" ( |
||
|
The reasoning is the same as for "occurs in" |
-
BFO distinguishes between continuants & occurrants, which spatial region & spatiotemporal region are subclasses of, respectively. GeoSPARQL has no handling of temporality, so cannot yet map to any continuants
-
a future version of GeoSPARQL that handled spatio-temporal Features could perhaps claim that
geo:Featureis ardfs:subClassOfobo:BFO_0000011"spatiotemporal region", however inconsistencies from this mapping will occur due to the current Feature/"spatial region" mapping above and this will need to be handled
-
Annex F - CQL / GeoSPARQL Mapping (informative)
F.1 Accessing spatial Features in a SPARQL endpoint
Spatial Features accessed via SPARQL endpoints [SPARQLPROT] are, as defined in the GeoSPARQL standard, instances of the OWL class geo:Feature or of subclasses of it.
They may have one or more geo:hasGeometry properties indicating geo:Geometry instances and other properties related to the Feature. They may also be grouped into geo:FeatureCollection instances where geo:FeatureCollection is a new class in GeoSPARQL 1.1, specifically for the description of collections of geo:Feature instances.
The following example SPARQL query retrieves all Features within the Feature Collection with the IRI ex:x within a given SPARQL endpoint.
SELECT ?fcollection ?item ?rel ?val ?geom
WHERE {
ex:x rdfs:member ?item .
?item rdfs:subClassOf* geo:Feature .
}GeoSPARQL’s geo:FeatureCollection definition requires that geo:Feature instances are to be linked to the Collection by use of the rdf:member property. No inverse property is defined.
|
Note
|
Some CQL-implementing systems, such as OGC API, have fixed notions of Feature Collections and require that Features be members of exactly one Feature Collection. There is no such restriction in GeoSPARQL: Features may be members of one or more Feature Collections. |
An extension to the above can retrieve any Geometry serializations for the Features within Feature Collection ex:x:
SELECT ?fcollection ?item ?rel ?val ?geom
WHERE {
ex:x rdfs:member ?item .
?item rdfs:subClassOf* geo:Feature .
OPTIONAL {
?item geo:hasGeometry/geo:hasSerialization ?geom
}
}Some additional concerns for GeoSPARQL / CQL or OGC API Features Feature Collections mappings are:
-
APIs may need more information about the
geo:FeatureCollectioninstance for correct handling, in particular, an identifier and perhaps a label. If the back-end data store also contains information for thegeo:FeatureCollectioninstance then this may be queried for. If not, the API might need to create such data-
One particular scenario observed is that OGC APIs require token-like identifiers for Feature Collections and GeoSPARQL IRIs, or their parts, may not be able to be used for such. In these cases, the RDF property
dcterms:identifiermay be used to store appropriate token-like identifiers
-
-
Perhaps only data in a certain namespace is of interest. The solution is to apply FILTER expressions to the SPARQL query
F.2 Mappings from CQL2 statements to GeoSPARQL queries
This section presents lists of equivalences between Common Query Language (CQL2) [CQLDEF] statements and GeoSPARQL statements.
F.2.1 Query Parameters
Several query parameters may be given as parameters to the HTTP request of CD-implementing systems, such as the OGC API Features service. These parameters have an influence on the SPARQL query to be executed for the retrieval of a FeatureCollection to be exposed using an OGC API Features service.
| Query Parameter | Example | SPARQL Expression | Example | Comment |
|---|---|---|---|---|
limit |
limit=5 |
LIMIT |
LIMIT 5 |
|
offset |
offset=10 |
OFFSET |
OFFSET 10 |
|
bbox |
|
|
|
WKT does not define a type boundingbox, therefore a bbox is converted to a Polygon |
datetime |
|
- |
- |
GeoSPARQL doesn’t detail temporal aspects of data. Filtering data using RDF temporal properties may be achieved using basic SPARQL queries and also OWL TIME [TIME] |
F.2.2 Literal Values
CQL2 defines literal values for a variety of datatypes. The following table shows the equivalences of these values in RDF which may be used in any GeoSPARQL query.
| CQL2 literal | Examples | (Geo)SPARQL literal | Examples |
|---|---|---|---|
String |
"This is a string" |
"This is a string"^^xsd:string |
|
Number |
-100 3.14159 |
"-100"^^xsd:integer "3.14159"^^xsd:double |
|
Boolean |
true false |
"true"^^xsd:boolean "false"^^xsd:boolean |
|
Spatial Geometry (WKT) |
POINT(1 1) |
"POINT(1 1)"^^geo:wktLiteral |
|
Spatial Geometry (JSON) |
{"type": "Point", "coordinates":[1,1]} |
"{"type": "Point", "coordinates":[1,1]}"^^geo:geoJSONLiteral |
|
Temporal Literal |
1969-07-20 1969-07-20T20:17:40Z |
"1969-07-20"^^xsd:date "1969-07-20T20:17:40Z"^^xsd:dateTime |
F.2.3 Property references
CQL2 allows the referencing of properties in a Feature Collection it is targeting for filtering. A property reference is converted to a triple pattern as shown in the following example. A SPARQL variable ?item is assumed to represent the Feature Collection.
| Property Reference | Triple pattern |
|---|---|
name="OGC" |
|
number=5 |
|
number>5 |
|
F.2.4 Comparison Predicates
CQL2 defines comparison predicates to compare two scalar expressions. A comparison predicate is converted to a triple pattern as shown in the following example. A SPARQL variable ?item is assumed to represent the Feature Collection.
| Comparison predicate | Triple pattern | Comment |
|---|---|---|
name="OGC" |
|
Equality statements can be converted to a triple pattern |
number=5 |
|
|
number>5 |
?item my:number ?number . FILTER(?number>5) |
Arithmetic comparisons (<,>,>=,⇐) are converted to filter expressions |
number BETWEEN 5 AND 10 |
|
BETWEEN statements are converted to arithmetic expressions |
name IN ("OGC","W3C") |
|
IN statements may also be expressed using SPARQL VALUES statements |
name IS NOT NULL |
|
NOT NULL statements are converted to EXIST statements |
name LIKE "OGC." |
|
LIKE statements are converted to SPARQL regex filters |
INTERSECTS(geometry1, geometry2) |
|
The INTERSECTS filter statement is converted to a GeoSPARQL FILTER statement |
There is no direct GeoSPARQL equivalent to a CRS-based CQL filter, however certain GeoSPARQL geometry literals have explicity CRS/SRS information that may be filtered using SPARQL REGEX operators.
F.2.5 Spatial Operators
GeoSPARQL includes equivalents of many CQL2 filter functions as can be seen in the table below.
| CQL2 Filter Expression | GeoSPARQL Filter Function |
|---|---|
CONTAINS(geometry1,geometry2) |
FILTER(geof:sfContains(?geometry1,?geometry2)) |
CROSSES(geometry1,geometry2) |
FILTER(geof:sfCrosses(?geometry1,?geometry2)) |
DISJOINT(geometry1,geometry2) |
FILTER(geof:sfDisjoint(?geometry1,?geometry2)) |
EQUALS(geometry1,geometry2) |
FILTER(geof:sfEquals(?geometry1,?geometry2)) |
INTERSECTS(geometry1,geometry2) |
FILTER(geof:sfIntersects(?geometry1,?geometry2)) |
OVERLAPS(geometry1,geometry2) |
FILTER(geof:sfOverlaps(?geometry1,?geometry2)) |
TOUCHES(geometry1,geometry2) |
FILTER(geof:sfTouches(?geometry1,?geometry2)) |
WITHIN(geometry1,geometry2) |
FILTER(geof:sfWithin(?geometry1,?geometry2)) |
F.2.6 Temporal Operators
Temporal operators are not part of the GeoSPARQL standard.
| CQL2 Filter Expression | GeoSPARQL Filter Function |
|---|---|
beginTime AFTER 1969-07-16T13:32:00Z |
N/A |
beginTime BEFORE 1969-07-16T13:32:00Z |
N/A |
beginTime BEGINS 1969-07-16T13:32:00Z |
N/A |
beginTime BEGUNBY 1969-07-16T13:32:00Z |
N/A |
beginTime DURING 1969-07-16T13:32:00Z |
N/A |
beginTime ENDEDBY 1969-07-16T13:32:00Z |
N/A |
beginTime ENDS 1969-07-16T13:32:00Z |
N/A |
beginTime MEETS 1969-07-16T13:32:00Z |
N/A |
beginTime METBY 1969-07-16T13:32:00Z |
N/A |
beginTime OVERLAPPEDBY 1969-07-16T13:32:00Z |
N/A |
beginTime TCONTAINS 1969-07-16T13:32:00Z |
N/A |
beginTime TEQUALS 1969-07-16T13:32:00Z |
N/A |
beginTime TOVERLAPS 1969-07-16T13:32:00Z |
N/A |
As noted above in Section F.2.1 Query Parameters, temporal filtering of RDF data via SPARQL queries is possible with standard SPARQL functions to compare date values (xsd:date, xsd:dateTime and xsd:dateTimeStamp literals) and OWL TIME [TIME] may be used to assert temporal relations between objects.
F.3 Mappings from Simple Features for SQL
The following table maps the functions and properties from Simple Features for SQL [OGCSFACA] [ISO19125-1] to GeoSPARQL.
| Simple Features for SQL | GeoSPARQL Equivalent | Since GeoSPARQL | Related Property Available | Since GeoSPARQL |
|---|---|---|---|---|
2.1.1.1 Basic Methods on Geometry |
||||
Dimension(): Double |
|
- |
|
1.0 |
GeometryType(): Integer |
Class of geometry instance |
1.0 |
N/A |
- |
SRID(): Integer |
|
1.0 |
N/A |
- |
Envelope(): Geometry |
|
1.0 |
|
1.1 |
AsText(): String |
|
1.1 |
|
1.0 |
AsBinary(): Binary |
N/A |
- |
N/A |
- |
IsEmpty(): Integer |
|
- |
|
1.0 |
IsSimple(): Integer |
|
- |
|
1.0 |
Boundary(): Geometry |
|
1.0 |
N/A |
- |
2.1.1.2 Spatial Relations |
||||
Equals(anotherGeometry: Geometry): Integer |
|
1.0 |
|
1.0 |
Disjoint(anotherGeometry: Geometry): Integer |
|
1.0 |
|
1.0 |
Intersects(anotherGeometry: Geometry): Integer |
|
1.0 |
|
1.0 |
Touches(anotherGeometry: Geometry): Integer |
|
1.0 |
|
1.0 |
Crosses(anotherGeometry: Geometry): Integer |
|
1.0 |
|
1.0 |
Within(anotherGeometry: Geometry): Integer |
|
1.0 |
|
1.0 |
Contains(anotherGeometry: Geometry): Integer |
|
1.0 |
|
1.0 |
Overlaps(anotherGeometry: Geometry): Integer |
|
1.0 |
|
1.0 |
Relate(anotherGeometry: Geometry, IntersectionPatternMatrix: String): Integer |
|
1.0 |
N/A |
- |
2.1.1.3 Spatial Analysis |
||||
Buffer(distance: Double): Geometry |
|
1.0 |
N/A |
- |
ConvexHull(): Geometry |
|
1.0 |
N/A |
- |
Intersection(anotherGeometry: Geometry): Geometry |
|
1.0 |
N/A |
- |
Union(anotherGeometry: Geometry): Geometry |
|
1.0 |
N/A |
- |
Difference(anotherGeometry: Geometry): Geometry |
|
1.0 |
N/A |
- |
SymDifference(anotherGeometry: Geometry): Geometry |
|
1.0 |
N/A |
- |
2.1.2.1 GeometryCollection |
||||
NumGeometries(): Integer |
|
- |
N/A |
- |
GeometryN(N: Integer): Geometry |
|
- |
N/A |
- |
2.1.3.1 Point |
||||
X(): Double |
N/A |
- |
N/A |
- |
Y(): Double |
N/A |
- |
N/A |
- |
Z(): Double (not in the SQL spec, but a logical extension) |
N/A |
- |
N/A |
- |
M(): Double (not in the SQL spec, but a logical extension) |
N/A |
- |
N/A |
- |
2.1.5.1 Curve |
||||
Length(): Double |
|
- |
|
1.1 |
StartPoint(): Point |
N/A |
- |
N/A |
- |
EndPoint(): Point |
N/A |
- |
N/A |
- |
IsClosed(): Integer |
N/A |
- |
N/A |
- |
IsRing(): Integer |
N/A |
- |
N/A |
- |
2.1.6.1 LineString |
||||
NumPoints(): Integer |
N/A |
- |
N/A |
- |
PointN(N: Integer): Point |
N/A |
- |
N/A |
- |
2.1.7.1 MultiCurve |
||||
IsClosed(): Integer |
N/A |
- |
N/A |
- |
Length(): Double |
|
- |
|
1.1 |
2.1.9.1 Surface |
||||
Area(): Double |
|
- |
|
1.1 |
Centroid(): Point |
|
1.1 |
|
1.1 |
PointOnSurface(): Point |
N/A |
- |
N/A |
- |
2.1.10.1 Polygon |
||||
ExteriorRing(): LineString |
N/A |
- |
N/A |
- |
NumInteriorRing(): Integer |
N/A |
- |
N/A |
- |
InteriorRingN(N: Integer): LineString |
N/A |
- |
N/A |
- |
2.1.11.1 MultiSurface |
||||
Area(): Double |
|
- |
|
1.1 |
Centroid(): Point |
|
1.1 |
|
1.1 |
PointOnSurface(): Point |
N/A |
- |
N/A |
- |
Annex G - Revision History
| Date | Release | Author | Paragraph modified | Description |
|---|---|---|---|---|
27 Oct. 2009 |
Draft |
Matthew Perry |
Clause 6 |
Technical Draft |
11 Nov. 2009 |
Draft |
John R. Herring |
All |
Creation |
06 Jan. 2010 |
Draft |
John R. Herring |
All |
Comment responses |
30 March 2010 |
Draft |
Matthew Perry |
All |
Comment responses |
26 Oct. 2010 |
Draft |
Matthew Perry |
All |
Revision based on working group discussion |
28 Jan. 2011 |
Draft |
Matthew Perry |
All |
Revision based on working group discussion |
18 April 2011 |
Draft |
Matthew Perry |
All |
Restructure with multiple conformance classes |
02 May 2011 |
Draft |
Matthew Perry |
Clause 6 and Clause 8 |
Move Geometry Class from core to geometryExtension |
05 May 2011 |
Draft |
Matthew Perry |
All |
Update URIs |
13 Jan. 2012 |
Draft |
Matthew Perry |
All |
Revision based on Public RFC |
16 April 2012 |
Draft |
Matthew Perry |
All |
Revision based on adoption vote comments |
19 July 2012 |
1.0 |
Matthew Perry |
All |
Revision of URIs based on OGC Naming Authority recommendations |
09 Oct. 2020 |
1.1 Draft |
Joseph Abhayaratna |
All |
Establishment of the 1.1 Specification |
10 Oct. 2020 to 02 June. 2022 |
1.1 Draft |
GeoSPARQL 1.1 SWG |
All |
Addition of GeoSPARQL 1.1 elements |
23 Oct. 2022 |
1.1 For Public Comment |
Karl Reed, Joseph Abhayaratna |
All |
Final review prior to public comment |
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