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. (
  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:
  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:
  7. 7. Linked data simplifies much of the complexity of the Semantic Web 7Image:
  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 8
  9. 9. Is it used somewhere as well? Ja! More datasets available at‐sets LOD on the Web Visualization :‐ 9 open‐data‐on‐the‐web‐visualization/
  10. 10. Class relations amongst datasets 10
  11. 11. Instance relations amongst datasets 11
  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‐ rdf:type foaf:member foaf:name “Werner Kuhn” foaf:name http://ifgi.uni‐ rdf:type foaf:name l A foaf:topic interestowl:sameAs http://www.informatik.uni‐‐ t /k/K h W ht l h //db di / /S i S W b foaf:topic_interest 13 tree/k/Kuhn:Werner.html
  14. 14. PREFIX foaf:   PREFIX dc:   CONSTRUCT    http://ifgi‐  foaf:made ?paper    WHERE    ?paper a foaf:Document .  ?paper dc:creator   14
  15. 15. Linked Data Browsers, Mashups and other Client ApplicationsApplications 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/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:
  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?