1. OGC GeoSPARQL: Standardizing Spatial Query on the Semantic Web
Matthew Perry, Oracle
4th Annual Spatial Ontology Community of Practice Workshop
USGS, Sunrise Valley Drive , Reston VA
December 2, 2011

2. Agenda About the OGC GeoSPARQL SWG Overview of GeoSPARQL GeoSPARQL FAQ
Use Cases
GeoSPARQL Vocabulary
Query Functions
Entailment Components
GeoSPARQL FAQ
Future Work

3. THE FOLLOWING IS INTENDED TO OUTLINE OUR GENERAL PRODUCT DIRECTION
THE FOLLOWING IS INTENDED TO OUTLINE OUR GENERAL PRODUCT DIRECTION. IT IS INTENDED FOR INFORMATION PURPOSES ONLY, AND MAY NOT BE INCORPORATED INTO ANY CONTRACT. IT IS NOT A COMMITMENT TO DELIVER ANY MATERIAL, CODE, OR FUNCTIONALITY, AND SHOULD NOT BE RELIED UPON IN MAKING PURCHASING DECISION. THE DEVELOPMENT, RELEASE, AND TIMING OF ANY FEATURES OR FUNCTIONALITY DESCRIBED FOR ORACLE'S PRODUCTS REMAINS AT THE SOLE DISCRETION OF ORACLE. 3

4. About the OGC GeoSPARQL SWG

5. Group Members Open Geospatial Consortium standards working group
13 voting members, 36 observers
Editors: Matthew Perry and John Herring
Chairs: John Herring and Dave Kolas
Submitting Organizations
Australian Bureau of Meteorology
Bentley Systems, Inc.
CSIRO
Defence Geospatial Information Working Group (DGIWG)
GeoConnections - Natural Resources Canada
Interactive Instruments GmbH
Oracle America
Ordnance Survey
Raytheon Company
Traverse Technologies, Inc.
US Geological Survey (USGS)

6. Standardization Process
Form SWG (June 2010)
Release candidate standard (May 2011)
OAB vote on candidate standard (June 2011)
30-day public comment period (July 2011)
Process comments and update document (Now)
TC/PC vote on final document
Publish standard

7. GeoSPARQL Overview

8. Some Use Cases Existing LOD RDF datasets with some simple spatial data
DBPedia, GeoNames, etc.
Mainly simple, WGS84 Lat Long points
GIS applications with semantically complex thematic aspects
Reasoning based on complex land cover type hierarchy
Qualitative reasoning applications without explicit geometries
RCC8-based reasoning
Data integration applications
RDB2RDF + Federated SPARQL over spatial datasets

9. Goals for GeoSPARQL Provide a common target for implementers & users
Oracle, BBN Parliament, Virtuoso, OWLIM, Franz, …
Work within SPARQL’s extensibility framework
Simple enough for general users but capable enough for GIS professionals
Accommodate systems based on qualitative spatial reasoning and systems based on quantitative geometries
Don’t re-invent the wheel!
Simple Features
Well Known Text (WKT)
GML
KML
GeoJSON
ISO – Spatial Schema
ISO – SQL/MM

10. A Simple Example
:OGCSept2011TC :locatedIn :Reston .
:Reston :hasPointGeometry [
ogc:asWKT “POINT( )”^^ogc:WKTLiteral ] .
Example Data: December 2011 SOCoP Workshop is located in Reston, VA
SELECT ?airport
WHERE { ?airport rdf:type :Airport .
?airport :hasPointGeometry [
ogc:asWKT ?aPointGeom ]
FILTER(ogcf:distance(?aPointGeom,
“POINT( )”^^ogc:WKTLiteral,
ogc:km) <= 100) }
Example Query: Find airports within 100 KM of Reston, VA

11. What Does GeoSPARQL Give Us?
Vocabulary for Query Patterns
Classes
Spatial Object, Feature, Geometry
Properties
Topological relations
Links between features and geometries
Datatypes for geometry literals
ogc:WKTLiteral, ogc:GMLLiteral
Query Functions
Topological relations, distance, buffer, intersection, …
Entailment Components
RIF rules to expand feature-feature query into geometry query
Gives a common interface for qualitative and quantitative systems

12. Some Features of the Spec
Uses a Modular Design
Consists of several components
It’s Parameterized
Serialization: WKT, GML, KML, …
Relation Family: Simple Features, Egenhofer, RCC8, …
Benefits
Vendors can easily identify what they support
We support components X, Y and Z for WKT and GML serializations and Simple Features relations
Extensible
Can easily add new components
Can easily add new spatial relations and serializations

13. GeoSPARQL Vocabulary

14. GeoSPARQL Vocabulary: Basic Classes and Relations
ogc:SpatialObject
Same as ISO
GM_Object
ogc:hasGeometry
0 .. *
ogc:Feature
ogc:Geometry
ogc:dimension : xsd:int
ogc:coordinateDimension : xsd:int
ogc:spatialDimension : xsd:int
ogc:isEmpty : xsd:boolean
ogc:isSimple : xsd:boolean
ogc:asWKT : ogc:WKTLiteral
ogc:asGML : ogc:GMLLiteral …
0 .. 1
metadata
ogc:hasDefaultGeometry
Same as ISO
GFI_Feature
serializations
Geometry encoded as a Literal

15. Details of ogc:WKTLiteral
All RDFS Literals of type ogc:WKTLiteral shall consist of an optional IRI identifying the spatial reference system followed by Simple Features Well Known Text (WKT) describing a geometric value [ISO ].
“< POINT( )”^^ogc:WKTLiteral
WGS84 longitude – latitude is the default CRS
“POINT( )”^^ogc:WKTLiteral
European Petroleum Survey Group (EPSG) maintains a set of CRS identifiers.

16. Details of ogc:GMLLiteral
All ogc:GMLLiterals shall consist of a valid element from the GML schema that implements a subtype of GM_Object as defined in [OGC ].
"<gml:Point
srsName=\"
xmlns:gml=\"
<gml:pos> </gml:pos>
</gml:Point>"^^ogc:GMLLiteral
Note that GMLLiterals are NOT rdf:XMLLiterals

17. Topological Relations between ogc:SpatialObject
A/B A B A B B
ogc:sfEquals
ogc:sfTouches
ogc:sfOverlaps
ogc:sfContains A B A B A B B A
ogc:sfWithin
ogc:sfDisjoint
ogc:sfIntersects
ogc:sfCrosses
Assumes Simple Features Relation Family

18. RCC8, Egenhofer & Simple Features
equals
equal EQ
disjoint DC
intersects
¬ disjoint
¬ DC
touches
meet EC
within
inside+coveredBy
NTPP+TPP
contains
contains+covers
NTPPi+TPPi
overlaps
overlap PO

19. Example Data Meta Information Non-spatial Properties
:City rdfs:subClassOf ogc:Feature .
:Park rdfs:subClassOf ogc:Feature .
:exactGeometry rdfs:subPropertyOf ogc:hasGeometry .
:Nashua rdf:type :City .
:MinesFallsPark rdf:type :Park .
:MinesFallsPark :opened “ ”^^xsd:date .
:MinesFallsPark :exactGeometry :geo1 .
:geo1 ogc:asWKT “Polygon((…))”^^ogc:WKTLiteral .
:Nashua :exactGeometry :geo2 .
:geo2 ogc:asWKT “Polygon((…))”^^ogc:WKTLiteral .
:MinesFallsPark ogc:sfWithin :Nashua .
Non-spatial Properties
Spatial Properties

20. GeoSPARQL Query Functions

21. GeoSPARQL Query Functions
ogcf:distance(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral, units: xsd:anyURI): xsd:double
ogcf:buffer(geom: ogc:WKTLiteral, radius: xsd:double,
units: xsd:anyURI): ogc:WKTLiteral
ogcf:convexHull(geom: ogc:WKTLiteral): ogc:WKTLiteral
geom1
geom2
geom
geom

22. GeoSPARQL Query Functions
ogcf:intersection(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): ogc:WKTLiteral
ogcf:union(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): ogc:WKTLiteral
geom2
geom1
geom2
geom1

23. GeoSPARQL Query Functions
ogcf:difference(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): ogc:WKTLiteral
ogcf:symDifference(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): ogc:WKTLiteral
geom2
geom1
geom2
geom1

24. GeoSPARQL Query Functions
ogcf:envelope(geom: ogc:WKTLiteral): ogc:WKTLiteral
ogcf:boundary(geom1: ogc:WKTLiteral): ogc:WKTLiteral
ogcf:getSRID(geom: ogc:WKTLiteral): xsd:anyURI
geom
geom

25. GeoSPARQL Topological Query Functions
ogcf:relate(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral, patternMatrix: xsd:string): xsd:boolean
DE-9IM Intersection Matrix
geom2
Interior
Boundary
Exterior
geom1 T F
geom1
geom2
ogc:contains
patternMatrix: TTTFFTFFT

26. GeoSPARQL Topological Query Functions
ogcf:sfEquals(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): xsd:boolean
ogcf:sfDisjoint(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): xsd:boolean
ogcf:sfIntersects(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): xsd:boolean
ogcf:sfTouches(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): xsd:boolean
ogcf:sfCrosses(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): xsd:boolean
ogcf:sfWithin(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): xsd:boolean
ogcf:sfContains(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): xsd:boolean
ogcf:sfOverlaps(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): xsd:boolean
Assumes Simple Features Relation Family

27. Example Query
Find all land parcels that are within the intersection of :City1 and :District1
PREFIX : <
PREFIX ogc: <
PREFIX ogcf: <
PREFIX epsg: <
SELECT ?parcel
WHERE { ?parcel rdf:type :Residential .
?parcel :exactGeometry ?pGeo .
?pGeo ogc:asWKT ?pWKT .
:District1 :exactGeometry ?dGeo .
?dGeo ogc:asWKT ?dWKT .
:City :extent ?cGeo .
?cGeo ogc:asWKT ?cWKT .
FILTER(ogcf:sfWithin(?pWKT,
ogcf:intersection(?dWKT,?cWKT)))}

28. Example Query Find the three closest Mexican restaurants
PREFIX : <
PREFIX ogc: <
PREFIX ogcf: <
PREFIX epsg: <
SELECT ?restaurant
WHERE { ?restaurant rdf:type :Restaurant .
?restaurant :cuisine :Mexican .
?restaurant :pointGeometry ?rGeo .
?rGeo ogc:asWKT ?rWKT }
ORDER BY ASC(ogcf:distance(“POINT(…)”^^ogc:WKTLiteral,
?rWKT, ogc:KM))
LIMIT 3

29. GeoSPARQL Entailment Components

30. GeoSPARQL RDFS Entailment Extension
Main Requirements:
Basic graph pattern matching shall use the semantics defined by the RDFS Entailment Regime [W3C SPARQL Entailment]
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 / GML

31. Simple Features Geometry Types
ogc:Geometry
ogc:Point
ogc:Curve
ogc:Surface
ogc:GeometryCollection
ogc:LineString
ogc:Polygon
ogc:PolyhedralSurface
ogc:MultiSurface
ogc:MultiCurve
ogc:MultiPoint
ogc:Triangle
ogc:TIN
ogc:Line
ogc:LinearRing
ogc:MultiPolygon
ogc:MultiLineString

32. GeoSPARQL Query Rewrite Extension
Find all water bodies within New Hampshire
SELECT ?water
WHERE { ?water rdf:type :WaterBody .
?water ogc:rcc8Within :NH }
RCC8 Backward Chaining
SELECT ?water
WHERE { ?water rdf:type :WaterBody .
?water ogc:hasDefaultGeometry ?wGeo .
?wGeo ogc:asWKT ?wWKT .
:NH ogc:hasDefaultGeometry ?nGeo .
?nGeo ogc:asWKT ?nWKT .
FILTER(ogcf:rcc8Within(?wWKT, ?nWKT)) }
Same Query Specification
Qualitative
Quantitative
Query Rewrite
Specified with a RIF rule

33. GeoSPARQL Query Rewrite Extension
Main Requirement:
Basic graph pattern matching shall use the semantics defined by the RIF Core Entailment Regime [W3C SPARQL Entailment] for the RIF rules [W3C RIF Core] geor:sf-equals, geor:sf-disjoint, geor:sf-intersects, geor:sf-touches, geor:sf-crosses, geor:sf-within, geor:sf-contains, geor:sf-overlaps.

34. Query Rewrite Rules
Used to compute Feature-Feature spatial relations based on default geometries
Specified as a collection of RIF rules
Example: ogcr:sfEquals
(Forall ?f1 ?f2 ?g1 ?g2 ?g1Serial ?g2Serial
(f1[ogc:sfEquals->?f2] :-
And
(?f1[ogc:hasDefaultGeometry->?g1]
?f2[ogc:hasDefaultGeometry->?g2]
?g1[ogc:asWKT->?g1Serial]
?g2[ogc:asWKT->?g2Serial]
External(ogcf:sfEquals(?g1Serial,?g2Serial))) )

35. Summary of Conformance Classes
Parameters
Core
Serialization
WKT
GML
Relation Family
Simple Features
RCC8
Egenhofer
Topology Vocabulary Extension (relation_family)
Geometry Extension (serialization, version)
Determines geometry
classes and geometry
literal datatype
Geometry Topology Extension (serialization, version, relation_family)
Query Rewrite Extension (serialization, version, relation_family)
RDFS Entailment Extension (serialization, version, relation_family)
Determines topology
properties and
topology functions

36. GeoSPARQL FAQ

37. Why don’t you have ogc:myFavoriteProperty?
GeoSPARQL vocabulary is not comprehensive
Just enough to define a reasonable set of query patterns
There are other efforts for more comprehensive vocabularies
ISO / TC 211
SOCoP
GeoVocamps
GeoSPARQL vocabulary can easily be extended with other application/domain-specific vocabularies

38. Why Encode Geometry Data as a Literal?
Advantage: single self-contained unit
Consistent way to select geometry information
Find all water bodies that are within 1 km of Route 3
SELECT ?water ?wWKT
WHERE { ?water rdf:type :WaterBody .
?water :hasExactGeometry ?wGeo .
?wGeo ogc:asWKT ?wWKT .
:Route_3 :hasExactGeometry ?r3Geo .
:r3Geo ogc:asWKT ?r3WKT .
FILTER(ogcf:distance(?r3WKT, ?wWKT,…) <= 1000) }
Consistent way to pass geometry information around

39. Why is SRID encoded in Geometry Literal?
The query functions need the SRID to perform computations
SRID is really a property of the serialization not fundamental to the geometry itself
GML already encodes it, only WKT has to be modified
Adding a separate property is redundant and potentially inconsistent
Note: geometry type class is also redundant but can be useful for entailment
We have an ogcf:getSRID() function to aid in filtering based on SRID

40. Why don’t you support W3C Basic Geo?
Too simple to meet our requirements
Can’t use different datums and coordinate systems
Limited number of geometry types
W3C Basic Geo data can easily be converted to WKTLiteral
PREFIX geo: <
PREFIX ogc: <
SELECT (STRDT(CONCAT("POINT(",?long," ",?lat,")"),
ogc:WKTLiteral) AS ?wktLit)
WHERE { ?point geo:long ?long .
?point geo:lat ?lat }

41. Can I support both GML and WKT?
YES
A valid GMLLiteral is an invalid WKTLiteral and vice versa
An operation on these two objects is an error according to the GeoSPARQL spec, but …
From Section of the SPARQL specification [W3C SPARQL] (
SPARQL language extensions may provide additional associations between operators and operator functions; this amounts to adding rows to the table above. No additional operator may yield a result that replaces any result other than a type error in the semantics defined above. The consequence of this rule is that SPARQL extensions will produce at least the same solutions as an unextended implementation, and may, for some queries, produce more solutions.

42. Why no Universal Geometry Ontology?
Geometry types in existing standards are different abstractions
e.g. Polygon edges can be arcs in ISO / GML but must be straight lines in Simple Features
Any hierarchy we get may be too restrictive
You should be able to conceptualize a geometry any way you want as long as you can support the required operations.
All we’re left with is a single root Geometry class in the core vocabulary
More detailed Geometry types are available with RDFS Entailment Extension
Supported Geometry types tied to serialization
Can’t use a geometry type if you can’t serialize it

43. Why do I have to support RDFS entailment?
Support for only geometry literals and query functions could be a popular use case
All entailment requirements are contained in a separate conformance class
RDFS Entailment Extension (serialization, version)
Query Rewrite Extension (serialization, version, relation_family)

44. Summary GeoSPARQL Defines: Based on existing OGC/ISO standards
Basic vocabulary, Query functions, Entailment component
Based on existing OGC/ISO standards
WKT, GML, Simple Features, ISO 19107
Uses SPARQL’s built-in extensibility framework
Modular specification
Allows flexibility in implementations
Easy to extend
Accommodates qualitative and quantitative systems
Same query specification for qualitative (core + topology vocabulary) and quantitative (all components, incl. query rewrite)

45. Future Work Define new conformance classes
KML, GeoJSON
Define OWL axioms for qualitative spatial reasoning
ogc:sfWithin rdf:type owl:TransitiveProperty
Hybrid qualitative / quantitative spatial reasoning
Define standard methodology for (virtually) converting legacy feature data represented using the general feature model to RDF (RDB2RDF for spatial)

46. Thanks to all members of the GeoSPARQL SWG !
Questions?

47. Find all water bodies that are within 1 km of Route 3
Example Queries
Find all water bodies that are within 1 km of Route 3
PREFIX : <
PREFIX ogc: <
PREFIX ogcf: <
PREFIX epsg: <
SELECT ?water ?wWKT
WHERE { ?water rdf:type :WaterBody .
?water :exactGeometry ?wGeo .
?wGeo ogc:asWKT ?wWKT .
:Route_3 :exactGeometry ?r3Geo .
:r3Geo ogc:asWKT ?r3WKT .
FILTER(ogcf:distance(?r3WKT, ?wWKT,
ogc:km) <= 1) }

48. Find all land parcels for sale within a constant search polygon
Example Queries
Find all land parcels for sale within a constant search polygon
PREFIX : <
PREFIX ogc: <
PREFIX ogcf: <
PREFIX epsg: <
SELECT ?parcel
WHERE { ?parcel rdf:type :Residential .
?parcel :for_sale “true”^^xsd:boolean .
?parcel :exactGeometry ?pGeo .
?pGeo :asWKT ?pWKT
FILTER(ogcf:within(?pWKT,
“Polygon((…))”^^ogc:WKTLiteral)) }

49. Non-topological Query Functions
ogcf:distance(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral, units: xsd:anyURI): xsd:double
ogcf:buffer(geom: ogc:WKTLiteral, radius: xsd:double,
units: xsd:anyURI): ogc:WKTLiteral
ogcf:convexHull(geom: ogc:WKTLiteral): ogc:WKTLiteral
ogcf:intersection(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): ogcf:WKTLiteral
ogcf:union(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): ogc:WKTLiteral
ogcf:difference(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): ogcf:WKTLiteral
ogcf:symDifference(geom1: ogc:WKTLiteral, geom2: ogc:WKTLiteral): ogc:WKTLiteral
ogcf:envelope(geom: ogc:WKTLiteral): ogcf:WKTLiteral
ogcf:boundary(geom1: ogc:WKTLiteral): ogc:WKTLiteral

50. OGC & ISO Geo Semantic Web Activities
GeoSPARQL Standards Working Group
Geosemantics Domain Working Group
ISO
ISO/RS 19150
Geographic information – Ontology
ISO rev
Geographic information – Reference model - Part 1: Fundamentals
ISO/PT
Geographic information – Ontology - Part 1: Framework
ISO/PT
Geographic information – Ontology - Part 2: Rules for developing ontologies in the Web Ontology Language (OWL)