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Brief State of the Art - Semantic Web technologies for geospatial data - Modelling and interoperability
The document discusses the importance of spatial information infrastructures and the semantic web in achieving interoperability for geographic data and services. It outlines challenges in data access, integration, and visualization and emphasizes the role of ontologies in managing semantic relationships among spatial data. The text highlights various methodologies and standards that support geospatial services and their integration within the semantic web framework.
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Brief State of the Art - Semantic Web technologies for geospatial data - Modelling and interoperability
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- 3. /37 Spatial Information Infrastructures SemanticWeb Spatial Semantic Web Introduction 3
- 4. / 35 Introduction –Spatial Information Infrastructures 4 Goals • Discover resources (data and services) • Access data (for both vector and coverage data) • Use data • Visualize data according to given rules • Harmonize and integrate data • Orchestration Challenges • Inconsistent data • Naming conflicts • Scale conflicts • Precision or resolution conflicts • Constraint conflicts • Data value conflicts • Multilinguality • Multiple representations • Reference systems and units of measure • Etc.
- 5. / 355 Introduction –The Semantic Web
- 6. / 356 Introduction –The Spatial Semantic Web Spatial data community • Ontologies for describing spatial data • Formally defined and shared semantics • Handling of heterogeneous spatial features Semantic Web community • Spatial information as a context provider • Data validity • Temporal information
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- 8. / 358 Semantic WebTechnologies for Information Infrastructures
- 9. / 359 A growingdemand for interoperability < 1970s • Mainframe computing • Centralized perspective 1980s • First revolution: advent of personal computer • Data interoperability becomes an issue 1990s • Second revolution: advent of Internet • Need for more principled mechanisms to ensure interoperability
- 10. / 3510 Different layersof interoperability • Concerns bottom layers of ISO/OSI network hierarchy; • Solved through hardware standards (Ethernet) and protocols (TCP/IP and HTTP). Physical interoperability • Concerns the syntactic form of exchanged messages; • Realized through XML and syntactic standards (HTML, WSDL, SOAP) Syntactic interoperability • Concerns the meaning of messages and Web pages; • Allows automatic machine processing of information (selection, composition, reasoning). Semantic interoperability
- 11. / 3511 Ontologies asbuilding bricks for the Semantic Web • Explicit and shared specification of a conceptualization of a given knowledge domain (T. R. Gruber. Toward principles for the design of ontologies used for knowledge sharing. Presented at the Padua workshop on Formal Ontology, March 1993) Ontology definition • Establish robust theoretical foundations for geographic information science • Three sets of foundational issues : • Conceptual issues; • Representational and logical issues; • Implementation issues. Ontologies for geographical information science
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- 13. / 3513 Flavors ofsemantic interoperability • Minimal shared amount of information – the fact expressed in the statement itself • Enabled by RDF (Resource Description Format) • Ex: Object “Berne” is related to object “Switzerland” by “being its capital”. Minimal semantic interoperability • Minimal set of beliefs on what two agents may infer after having exchanged a sentence • Enabled by RDF Schema • Ex: Shared ontology defining that capitals are cities, capitals are unique, etc. Extended semantic interoperability • Lower bound + upper bound on what agents may not believe after exchanging a sentence • Enabled by OWL (Web Ontology Language) • Ex: OWL shared ontology forbidding the belief of Zurich is also a Swiss capital. Full semantic interoperability
- 14. / 3514 Building bricksof the Semantic Web architecture
- 15. / 3515 RDF RessourceDescription Framework An RDF document is structured as an ensemble of triplets An RDF triplet is an association {subject, predicate, object} An RDF document is a labeled and oriented graph. Object – Author ROX639 URI – http://www.gsem.fr/authors#ROX639 Predicate – Creator URI – http://purl.org/dc/elements/1.1/creator Subject – Document no42305 URI – http://www.gsem.fr/documents#D42305
- 16. / 3516 OWL WebOntology Language Extension of RDF/RDFS languages Adds new concepts Specialization of RDF constructs
- 17. / 3517 Example –DBpedia Relation Finder http://relfinder.dbpedia.org/relfinder.html
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- 19. / 3519 Works relatedto semantics in geospatial information 2000 • Bishr - Ontology-based information modeling provides more cognitive foundation for information systems models + minimizes the problem of semantic heterogeneity. 2001 • Smith - Ontology of geographical categories – a catalogue of the prime geospatial concepts and categories shared in common by human subjects. 2003 • Hakimpour et al. - Architecture and methodology for geographical schema integration based on DL reasoning on sources ontologies and global schemas • Fonseca et al. – Formal framework mapping spatial ontologies to geographic conceptual schemas
- 20. / 3520 Works relatedto semantics in geospatial information 2004 • Hess and Iochpe – Methodology for semantic integration of geographic conceptual schemas; • Rodriguez and Egenhofer – Technique for calculating semantic similarity among spatial entities (Matching Distance Similarity Measure). 2005 • Schwering and Raubal – Query method based on spatial relations for integration of information sources (shared vocabulary mapped to ontologies); • Sotnykova et al. – Methodology for integration of spatio-temporal schemas, based on the MADS-compliant source ontology (translated into OWL DL). 2006 • Stoimenov et al. – Implementation of semantic mediators acting access points for several independent geoinformation sources; • Aerts et al. – Methodology for topographic databases integration based on OWL ontologies.
- 21. / 3521 Works relatedto semantics in geospatial information 2008 • Xu et al. – Algorithm for automatic geospatial service composition based on WordNet ontology dictionary; • Tang et al. – Methodology for conceiving geographic information ontologies, and proposition of an ontology-based discovery protocol for geographic information. 2009 • Van Hage et al. – Open-source SWI-Prolog extension providing spatial indexing capabilities and spatial/semantic query integration; • Janowicz et al. – Outline the need for a Semantic Enablement Layer for OGC services, and establish steps towards its establishment. 2010 • Parundekar et al. – Algorithm for aligning ontologies of geospatial sources (use of subsumption/equivalence relations and conjuction/restriction classes); • Wick et al. – Version 2.2.1 of the GeoNames Ontology (over 6.2 million geonames toponyms with an unique URI)
- 22. / 3522 Example –GeoNames Ontology http://www.geonames.org/
- 23. / 35 Example –DBpedia Mobile 23 Main features Illustration
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- 25. / 3525 Semantics forServices within Spatial Information Infrastructures
- 26. / 3526 Semantic modelingconsiderations for geoservices • Common ground of ontological concepts to which semantic descriptions of services should refer. Semantic interoperability frameworks • Geoservices perform geo-operations on various representations of features (spatial, temporal and thematic dimensions) Geoservices • Ontology-based : • Classification of geo-operation functionality; • Description of operation input and output parameter types; • Description of geodata that are tightly coupled to the service; • Description of the control flow in (virtual) composite operations. Semantic description of geoservices
- 27. / 3527 The OWL-Sontology Discovery InteractionExecution
- 28. / 35 Semantic InteroperabilityFramework for Geoservices – SIFGEO Operations that match a set of input and/or output parameter types Operations that fit an existing service chain with respect to their input and/or output parameter types Operations that are composed of operations that instantiate a given set of operation types Information/service concepts that are sub- or super-classes of a given concept Data sets that contain a specific feature type Feature concept Concepts for real-world phenomena and their relations ISO 19110 (Methodology for Feature Cataloguing) standard Feature symbol Elements forming a feature at a symbol level and their relations ISO General Feature Model Geo operation Operation types (behavior + input/ output parameters) + control flow elements = OPERA ISO 19119 (Services) 28 Typical queries (Find all…) Framework formal ontologies
- 29. / 3529 Example –SIFGEO for the Java volcano eruption – 1 Scope: create a service chain to identify the extent of mud eruption Input: 3 SPOT images from the volcano eruption Step 1: Creating the services SPOT image 1 SPOT image 2 SPOT image 3 Band rationing service = distinguish land-mud boundaries Slicing service = land-mud pixels’ classification Cross service = combining land-mud coverages into one Impact service = impact area calculus for 2 eruption periods
- 30. / 3530 Example –SIFGEO for the Java volcano eruption – 2 Step 2: Linking services to the OPERA ontology Step 3: create the OWL-S description for the service chain Band rationing service -> opera:CrossCalculate Slicing service -> subclass of opera:Classify Cross service -> opera:CrossConcatenate Impact service -> subclass of opera:Group EvaluateEruption ≡ ServiceChain <ServiceChain> BandRationing isOfType opera:CrossCalculate Slicing isOfType opera:Classify Cross isOfType opera:CrossConcatenate Impact isOfType opera:Group </ServiceChain>
- 31. / 35 Example –Extending OWL-S for context-aware semantic Web service discovery – 1 31 Service Service Profile Service Model Service Grounding Service Context ECommerce Service xsd:float Information Service Personal Service Emergency Service xsd:boolean hasValue*
- 32. / 3532 Example –Extending OWL-S for context-aware semantic Web service discovery – 2
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- 34. / 35 Geographic information • Developmentof SII • Risk of condemning the GI community to a specialist backwater. • Semantic Web technologies • Useful, interesting • Difficult to integrate • Geosemantic interoperability relies on standards Geosemantics • Geo ontology • Feature ontology • Feature type ontology • Spatial relationship ontology • Toponym ontology • Coordinate reference/spatial index ontology • Geodata set/metadata ontology • Spatial services ontology Standardization • Critical for SII • SII must support the evolution of geosemantics • Geosemantic standards are not completely “hopeless without,” but they are at least quite urgently “nice to have.” 34 Conclusion and perspectives
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