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Linked Geospatial Data Representation and Querying Tutorial

Learn about representing and querying linked geospatial data using stRDF, GeoSPARQL, and spatial analysis functions. Get detailed examples and explore topological relations and vocabulary extensions.

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Linked Geospatial Data Representation and Querying Tutorial

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  1. Representation and querying of linked geospatial data- tutorial KonstantinaBereta 10/02/2014

  2. Example in stRDF gag:Olympia gag:name"Ancient Olympia"; rdf:typegag:MunicipalCommunity . Spatial literal gag:Olympiagag:geometry "POLYGON((21.5 18.5, 23.5 18.5, 23.5 21, 21.5 21, 21.5 18.5)); <http://www.opengis.net/def/crs/EPSG/0/4326>"^^ strdf:WKT . Spatial data type 2

  3. Example in GeoSPARQL gag:Olympia rdf:typegag:MunicipalCommunity; gag:name"Ancient Olympia"; gag:population"184"^^xsd:int; geo:hasGeometryex:polygon1. ex:polygon1 rdf:typegeo:Geometry; geo:asWKT "POLYGON((21.5 18.5,23.5 18.5, 23.5 21,21.5 21,21.5 18.5)) "^^sf:wktLiteral. Property from Geometry extension Spatial literal Spatial data type 3

  4. stSPARQL: Geospatial SPARQL 1.1 • We define a SPARQL extension function for each function defined in the OpenGIS Simple Features Access standard • Basic functions • Get a property of a geometry • xsd:intstrdf:dimension(strdf:geometry A) • xsd:stringstrdf:geometryType(strdf:geometryA) • xsd:intstrdf:srid(strdf:geometry A) • Get the desired representation of a geometry • xsd:stringstrdf:asText(strdf:geometryA) • xsd:stringstrdf:asGML(strdf:geometryA) • Test whether a certain condition holds • xsd:booleanstrdf:isEmpty(strdf:geometryA) • xsd:booleanstrdf:isSimple(strdf:geometryA) 4

  5. stSPARQL: Geospatial SPARQL 1.1 • Functions for testing topological spatial relationships • OGC Simple Features Access • xsd:booleanstrdf:equals(strdf:geometryA, strdf:geometry B) • xsd:booleanstrdf:disjoint(strdf:geometryA, strdf:geometry B) • xsd:booleanstrdf:intersects(strdf:geometryA, strdf:geometry B) • xsd:booleanstrdf:touches(strdf:geometryA, strdf:geometry B) • xsd:booleanstrdf:crosses(strdf:geometryA, strdf:geometry B) • xsd:booleanstrdf:within(strdf:geometryA, strdf:geometry B) • xsd:booleanstrdf:contains(strdf:geometryA, strdf:geometry B) • xsd:booleanstrdf:overlaps(strdf:geometryA, strdf:geometry B) • xsd:booleanstrdf:relate(strdf:geometryA, strdf:geometry B, • xsd:stringintersectionPatternMatrix) • Egenhofer • RCC-8 5

  6. stSPARQL: Geospatial SPARQL 1.1 • Spatial analysis functions • Construct new geometric objects from existing geometric objects • strdf:geometrystrdf:boundary(strdf:geometry A) • strdf:geometrystrdf:envelope(strdf:geometry A) • strdf:geometrystrdf:convexHull(strdf:geometry A) • strdf:geometrystrdf:intersection(strdf:geometry A, strdf:geometry B) • strdf:geometrystrdf:union(strdf:geometry A, strdf:geometry B) • strdf:geometrystrdf:difference(strdf:geometry A, strdf:geometry B) • strdf:geometrystrdf:symDifference(strdf:geometry A, strdf:geometry B) • strdf:geometrystrdf:buffer(strdf:geometry A, xsd:double distance, xsd:anyURI units) • Spatial metric functions • xsd:floatstrdf:distance(strdf:geometry A, strdf:geometry B, xsd:anyURI units) • xsd:floatstrdf:area(strdf:geometry A) • Spatial aggregate functions • strdf:geometrystrdf:union(set of strdf:geometry A) • strdf:geometrystrdf:intersection(set of strdf:geometry A) • strdf:geometrystrdf:extent(set of strdf:geometryA) 6

  7. GeoSPARQL Topology Vocabulary Extension • The extension is parameterized by the family of topological relations supported. • Topological relations for simple features • The Egenhofer relations e.g., geo:ehMeet • The RCC-8 relations e.g., geo:rcc8ec 7

  8. The system Strabon • Data model: stRDF • Query language: stSPARQL/GeoSPARQL • Use of OGC standards(Well-Known Text and GML) 8

  9. The system Strabon (cont’d) WKT GML [ ISWC 2012 ] stRDFgraphs stSPARQL/ GeoSPARQL queries 9

  10. links • Strabon endpoint installation guide • Strabonwebsite • stSPARQLreference • Greek Linked Open Data datasets

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