KM Lecture 7 LOD

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Slides of the Knowledge and Media lecture about Linked Data and Linked Open Data. Presented 19 november 2012. Slides were based on presentations by Victor de Boer and Christophe Guéret

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KM Lecture 7 LOD

  1. 1. LECTURE 7: LINKED (OPEN) DATA Marieke van Erp(with slides from Victor de Boer and Christophe Guéret)
  2. 2. TODAY’S LECTURE• Why Linked (Open) Data?• What is Linked (Open) Data?• The story of Linked Open Data• Contributing to Linked Data• Standards and best practices• Consuming Linked Data• Drawbacks and problems
  3. 3. WHY LINKED DATA (1/2)Slide stolen from Christophe Guéret
  4. 4. WHY LINKED DATA (2/2)Slide stolen from Christophe Guéret
  5. 5. ``Sharable, spreadable and nerd-friendly’’ -- Charlotte S H Jensen,
  6. 6. WHAT IS LINKED DATA?• Linked Data is a method to publish structured data for interlinking with other data sources• Standard Web technology (HTTP and URIs)• Making information more easily readable and shareable for machines• Linked Open Data is a W3C community project to extend the Web with open data sets http://www.ted.com/talks/tim_berners_lee_on_the_next_web.html
  7. 7. THE STORY May 2007
  8. 8. Oct
  9. 9. “Linking Open Data cloud diagram, by Richard Cyganiak and Anja Jentzsch. http://lod-cloud.net/”
  10. 10. “Linking Open Data cloud diagram, by Richard Cyganiak and Anja Jentzsch. http://lod-cloud.net/”
  11. 11. CONTRIBUTING TO LINKED DATAYes, it may be scary to open upyour data but it may lead to: • Transparency • Participation • Improvement • Innovation • New knowledge & insights from combined data sources
  12. 12. STANDARDS AND BEST PRACTICES
  13. 13. LINKED OPEN DATA FIVE STAR SYSTEM Available on the web (whatever ★ format), but with an open license Available as machine-readable ★★ structured data (e.g. excel instead of image scan of a table) as (2) plus non-proprietary format (e.g. ★★★ CSV instead of excel) All the above plus, Use open standards from W3C (RDF and SPARQL) to ★★★★ identify things, so that people can point at your stuff All the above, plus: Link your data to ★★★★★ other people’s data to provide context www.w3.org/designissues/
  14. 14. FOUR RULES OF LINKED DATA1. Use URIs as names for things (Resources)2. Use HTTP URIs so that people can look up those names. (Dereferencing)3. When someone looks up a URI, provide useful information, using the standards (RDF*, SPARQL)4. Include links to other URIs. so that they can discover more things. http://www.w3.org/DesignIssues/
  15. 15. FOUR RULES OF LINKED DATA1. Use URIs as names for things (Resources)2. Use HTTP URIs so that people can look up those names. (Dereferencing)3. When someone looks up a URI, provide useful information, using the standards (RDF*, SPARQL)4. Include links to other URIs. so that they can discover more things. http://www.w3.org/DesignIssues/
  16. 16. HOW TO MAKE COOL URI’S• Use HTTP://• Use a namespace you control• Unique, stable and persistent• Don’t use: • Author name, subject, status, access, file name extension, software mechanism C://MyDisk/awesome/MvanErp/latest/cgi_bin/rembrandt.html
  17. 17. FOUR RULES OF LINKED DATA1. Use URIs as names for things2. Use HTTP URIs so that people can look up those names. (Dereferencing)3. When someone looks up a URI, provide useful information, using the standards (RDF*, SPARQL)4. Include links to other URIs. so that they can discover more things. http://www.w3.org/DesignIssues/
  18. 18. RDF REMINDERSubject     Predicate     Object   Triplesam:Rembrandt   am:hasBirthdate   “1651”am:Rembrandt   foaf:knows   am:PiterLastmanam:PiterLastman   am:wasBornIn   geonames:Amsterdam ate am:h asBir thd “1651” geonames:Amsterdam am:Rembrandt foaf:knows am:w asBorn In Graph am:PiterLastman
  19. 19. RDF CONVERSION <record priref="19319 “ > <date>1651</date><maker>Rembrandt (1606-1669)</maker> <object.type>etsplaat</object.type> … priref “19319 ” </record> date “1651” am:Record _:bn1 maker “Rembrandt (1606-1669)” object.type “etsplaat” “19319 ” iref :pr am am:date “1651” “1234” am:prirefam:Record am:maker am:Person am:birthdate am:proxy-19319 “1606” am:p-1234 rda:name “Rembrandt” am :obje ct.ty pe skos:Concept “etsplaat” am:etsplaat skos:prefLabel
  20. 20. ARCHITECTURE SPARQL-app Browser Purl.org redirect SPARQL Web interface HTTP server Logic a RDF(s) storage tri paclio Prolog http://
  21. 21. HOW TO ACCESS THE DATA• PURL 303 redirect to VU semantic layer http://purl.org/collections/nl/am/proxy-63432 è http://semanticweb.cs.vu.nl/europeana/browse/list_resource?r=http:// purl.org/collections/nl/am/proxy-63432• At our server: content negotiation • HTTP request text/html: • Local condensed view • Local full view • HTTP request application/rdf+xml • rdf/xml “describe”• SPARQL endpoint
  22. 22. TEXT/HTML
  23. 23. TEXT/HTML
  24. 24. APPLICATION/RDF+XML@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .@prefix ore: <http://www.openarchives.org/ore/terms/> .@prefix ens: <http://www.europeana.eu/schemas/edm/> .@prefix ahm: <http://purl.org/collections/nl/am/>ahm:proxy-66970 a ore:Proxy ; ahm:title "Zegelstempel Felix Meritis"@nl ; ahm:material ahm:t-12463 , ahm:t-5447 ; ahm:objectCategory ahm:t-5504 ; ahm:objectName ahm:t-13817 , ahm:t-8489 ; ahm:objectNumber "KA 7653.1" ; ahm:priref "66970" .ahm:proxy-66972 a ore:Proxy ; ahm:acquisitionDate "0000" ; ahm:title "Zegelstempel mogelijk van familiewapen"@nl .
  25. 25. SPARQLhttp://semanticweb.cs.vu.nl/europeana/user/query
  26. 26. FOUR RULES OF LINKED DATA1. Use URIs as names for things2. Use HTTP URIs so that people can look up those names.3. When someone looks up a URI, provide useful information, using the standards (RDF*, SPARQL)4. Include links to other URIs. so that they can discover more things. http://www.w3.org/DesignIssues/
  27. 27. LINK TO OTHER SOURCES “19319 ” iref :pr am am:date “1651” “1234” am:prirefam:Record am:maker am:Person am:birthdate “1606”am:proxy-19319 am:p-1234 rda:name “Rembrandt” owl:sameAs (?) Viaf:nationality “Dutch” Viaf:Person Viaf:RebrandtvanRijn “Rembrandt Harmensz. Van rdfs:label Rijn”
  28. 28. CONSUMING LINKED DATA• Generic Applications • Can process any data from any domain• Domain specific applications • Covers needs of specific user community
  29. 29. LINKED DATA BROWSERS
  30. 30. DOMAIN-SPECIFIC APPS
  31. 31. DRAWBACKS AND PROBLEMS• Extra burden on the data provider• Nerd-only (aka “SPARQL is hard”)• How do we build user-friendly systems?• Ranking, user-friendly information presentation• Scalability (how do you query a huge graph?)• Licenses • Is Open always a good idea? • Context?• Data quality
  32. 32. FURTHER READING• Tom Heath and Christian Bizer (2011) Linked Data: Evolving the Web into a Global Data Space (1st edition). Synthesis Lectures on the Semantic Web: Theory and Technology, 1:1, 1-136. Morgan & Claypool (available online for free)

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