Linked Data

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Lecture on Linked Data and Linked Geo-Data

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Linked Data

  1. 1. (Geospatial Semantics – Week 8) ANUSURIYA DEVARAJU Institute for Geoinformatics, University of Muenster.University of Muenster. (anusuriya.devaraju@uni-muenster.de)
  2. 2. Introduce the principles and key features of Linked Data(LD).( ) Describes the procedures to publish LD. Provides examples of existing datasets, tools available for publishing and using LD. Introduces the Linked Geo-Data, Linked Geo-Sensor data. 2
  3. 3. The Web of Documents – Documents are linked, but links are not qualified, q – Challenges : Querying across different sources; Information integration & discovery 3
  4. 4. Linked Data: The Web of data Goal : to share ‘data’ rather than ‘documents’ LD Browsers, Mashups, Search Engines Goal : to share data rather than documents Thing Thing Thing Thing RDF D t M d l Thing Thing Thing Thing RDF Data Model t d li k Data in various format typed linkstyped linkstyped linkstyped links format 4
  5. 5. The four rules… – Use URIs as names for things (anything not just documents)– Use URIs as names for things (anything, not just documents) – Use HTTP URIs so that people can look up those names. – When someone looks up a URI, provide useful information, using the standards (e g RDF SPARQL)standards (e.g., RDF, SPARQL) – Include RDF links to other URIs to enable the discovery of related information 5*Reference: http://www.w3.org/DesignIssues/LinkedData.html
  6. 6. Linked data is a style of publishing and interlinking structured data on the Web that : – Promotes reuse and reduces redundancy – Ease of discovery Ease of consumption due to standards based data sharing– Ease of consumption due to standards-based data sharing – Added value : build ecosystems around your data/content 6*Reference: http://www.ecom-icom.hku.hk/seminar/20100913/WhiteBebo.pdf
  7. 7. Linked data simplifies much of the complexity of the Semantic Web 7Image: http://bnode.org/media/2009/07/08/semantic_web_technology_stack.png
  8. 8. Community effort to publish existing datasets as Linked Data on the WebData on the Web Interlink things between different data sources Develop clients that consume Linked Data from the Webp 8http://esw.w3.org/SweoIG/TaskForces/CommunityProjects/LinkingOpenData
  9. 9. Is it used somewhere as well? Ja! More datasets available at http://linkeddata.org/data‐sets LOD on the Web Visualization : http://www.webknox.com/blog/2010/05/linked‐ 9 open‐data‐on‐the‐web‐visualization/
  10. 10. Class relations amongst datasets 10http://umbel.org/images/lod_constellation.html
  11. 11. Instance relations amongst datasets 11http://www4.wiwiss.fu-berlin.de/bizer/pub/lod-datasets_2009-07-14.html
  12. 12. 1. Triplification : convert existing data into RDF triples 12
  13. 13. 2. Identify co-referring entities into the RDF dataset 3. Linked to the Web of Linked Data3. Linked to the Web of Linked Data foaf:Groupfoaf:Group rdf:type “Muenster Semantic Interoperability Lab  MUSIL ” foaf:Person http://musil.uni‐muenster.de rdf:type foaf:member foaf:name “Werner Kuhn” foaf:name http://ifgi.uni‐muenster.de/kuhn rdf:type foaf:name l A foaf:topic interestowl:sameAs http://www.informatik.uni‐ trier.de/~ley/db/indices/a‐ t /k/K h W ht l h //db di / /S i S W b foaf:topic_interest 13 tree/k/Kuhn:Werner.html http://dbpedia.org/page/Semantic_Sensor_Web
  14. 14. PREFIX foaf:  http://xmlns.com/foaf/0.1/   PREFIX dc:  http://purl.org/dc/elements/1.1/   CONSTRUCT    http://ifgi‐muenster.de/kuhn  foaf:made ?paper    WHERE    ?paper a foaf:Document .  ?paper dc:creator http://dblp.l3s.de/d2r/resource/authors/Werner_Kuhn   14
  15. 15. Linked Data Browsers, Mashups and other Client ApplicationsApplications http://esw.w3.org/TaskForces/CommunityProjects/LinkingOpenData/SemWebC lients Linked Data Publishing Platforms/Frameworks D2R Server,  Pubby, Paget, Talis Platform, etc. Linked Data/RDF Editors and ValidatorsLinked Data/RDF Editors and Validators Hyena, Vapour Semantic Web Search Engines http://esw w3 org/TaskForces/CommunityProjects/LinkingOpenData/Semantichttp://esw.w3.org/TaskForces/CommunityProjects/LinkingOpenData/Semantic WebSearchEngines 15
  16. 16. Semantic Tagging and Rating 16Reference : Hausenblas M (2009), Linked Data Applications
  17. 17. Content Reuse 17
  18. 18. Integrated Question-Answering Systems 18
  19. 19. Event data management systems 19
  20. 20. Search Engines and Indexes 20
  21. 21. User Interfaces and Interaction Paradigms – Navigation controls in a LD browserg Application Architecture – Scalability problems with on-the-fly link traversal and federated queryingquerying Schema Mapping and Data Fusion – Resolving semantic conflicts (e.g., mix terminology from different vocabularies)vocabularies) Link maintenance – Dead links, informing link sources about changes via subscription modelsmodels 21Reference: Bizer C (2009), Linked Data – The Story So Far
  22. 22. Licensing : Data reused and republished Trust, Quality and RelevanceTrust, Quality and Relevance – Data relevant or appropriate to the user’s need – Integrated view of data provenance and trustworthiness PrivacyPrivacy – Higher awareness of the users about the data – Information accountability 22Reference: Bizer C (2009), Linked Data – The Story So Far
  23. 23. Adds spatial and temporal dimensions to the Web of Data. Links: geospatial web resourcesLinks: geospatial web resources unstructured /informal GI in the Web structured geo-databases scientific materials 23 structured geo databases (Different forms of Geographic Information on the Web)
  24. 24. 24* Vilches-Blázquez LM, et al. (2010), An Approach to Publish Spatial Data on the Web: The GeoLinked Data Case
  25. 25. Entity URIs are dereferenced via LD principles 25* Lopez-Pellicer (2010), Geo Linked Data
  26. 26. The content negotiation model of Linked Data is extended with support to Geoweb MIME-types.pp yp 26* Reference: Lopez-Pellicer J, et al. (2010), Geo Linked Data
  27. 27. Geonames – A geographical names database in RDF form.g g p Dbpedia – Contains location information which is interlinked with Geonames, the US Census Euro Stat and the CIA world fact bookthe US Census, Euro Stat and the CIA world fact book. LinkedGeoData – Data extracted from the Open Street Map project was linked to DBPedia instances using the links created by the users. Ordnance Survey – OS BoundaryLine product that contains all administrative areas plus– OS BoundaryLine product that contains all administrative areas plus legal boundaries. 27
  28. 28. 28Image: http://linkedgeodata.org/LGD%20Browser
  29. 29. Why Linked Sensor Data? – Increase the accessibility of non-OGC data sourcesy 29Reference : Kessler & Janowicz, (2010), Linking Sensor Data – Why, to What, and How?
  30. 30. Inclusion of spatial operators in the current Linked Data model to support complex queries.pp p q Transformation from geometries to an RDF-based representation adds complexity. N dl d d d t d t– Needless and redundant data ‘Browse’ pattern allows the discovery by subsequent links; ‘Query’ pattern is user specified [Schade & Lutz, 2010]Q y p p [ , ] How both approaches can be combined? Quality of links Undefined vocabulary terms, mismatched semantics, etc. 30Reference : Kessler & Janowicz, (2010), Linking Sensor Data – Why, to What, and How?

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