Creating Linked Data 2/5 Semtech2011


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Creating Linked Data 2/5 Semtech2011

  1. 1. Creating Linked Data<br />Juan F. Sequeda <br />Semantic Technology Conference<br />June 2011<br />
  2. 2. Linked Data is a set of best practices to publish and interlink data on the web<br />
  3. 3. Linked Data Principles<br />Use URIs as names for things<br />Use HTTP URIs so that people can look up (dereference) those names.<br />When someone looks up a URI, provide useful information.<br />Include links to other URIs so that they can discover more things.<br />
  4. 4. 1) Use URIs as names for things<br />
  5. 5. 1) Use URIs as names for things<br />Uniform Resource Identifiers identify real world objects and abstract concepts<br />Not only web documents and digital content<br />People, places, locations, my car<br />Know somebody, from somewhere<br />
  6. 6. 1) Use URIs as names for things<br /><br /><br /><br />
  7. 7. 1) Use URIs as names for things<br /><br />Identifies the person<br /><br />Identifies an RDF document<br />
  8. 8. 2) Use HTTP URIs so that people can look up (dereference) those names.<br />
  9. 9. 2) Use HTTP URIs so that people can look up (dereference) those names.<br />HTTP protocol is the Web’s universal access mechanism<br />Linked Data only uses HTTP URIs<br />URI: unique name<br />HTTP URI: universal means of access to the URI<br />HTTP URIs should be dereferencable<br />
  10. 10. Dereference a URI?<br />
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  16. 16. What’s with the redirection?<br />
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  28. 28. RDFa<br /><html><br />…<br /> <div xmlns:dc=“”><br /> <h2 property=“dc:title”>The trouble with Bob</h2><br /> <h3 property=“dc:creator”>Alice</h3><br /> ….<br /> </div><br />…<br /></html><br />
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  30. 30. Minting HTTP URIs<br />If you own the domain name and run a web server at that location, mint URIs in this namespace<br />I own the domain<br />I run a webserver<br />I now can mint URIs in this namespace:<br /><br />
  31. 31. Create Cool URIs<br />If you don’t control a namespace, don’t misuse it<br /><br />Avoid implementation details<br /><br />Use Natural Keys within URI<br /><br /><br />
  32. 32. Three different URIs<br />URI for the real world object (non-information resource)<br /><br /><br /><br /><br />URI for the HTML document (information resource) that describes the real world object<br /><br /><br /><br />URI for the RDF document (information resource) that describes the real world object<br /><br /><br /><br /><br />
  33. 33. 3) Provide useful information<br />
  34. 34. 3) Provide useful information<br />How do we provide useful information in document form on the web?  HTML<br />How do we provide useful information in data form on the web  RDF<br />Different ways of serializing RDF<br />RDF/XML<br />RDFa<br />N3<br />turtle<br />
  35. 35. RDF<br />subject – predicate – object<br />Coldplay is the artist of Viva la Vida<br />Coldplay is the artist of Viva la Vida<br /><br /><br /><br />
  36. 36. prefix dbpedia-owl: <><br />prefix foaf: <><br />prefix dbprop: <><br />prefix geo: <><br />51.507778<br />-0.128056<br />geo:long<br />geo:lat<br /><br />dbprop:origin<br /><br />dbpedia-owl:artist<br />foaf:name<br /><br />“Coldplay”<br />
  37. 37. ntriples<br /><> <> <> .<br /><> <> <> .<br />RDF/XML<br /><?xml version="1.0" encoding="utf-8"?><br /><rdf:RDFxmlns:rdf=""><br /><dbpedia-owl:Bandxmlns:dbpedia-owl=""<br />rdf:about=""><br /><dbpedia-owl:artistrdf:resource=""/> </dbpedia-owl:Band><br /></rdf:RDF><br />turtle<br />@prefix rdf: <> .<br /><><br /> a <> ;<br /><> <> .<br />
  38. 38. HTML<br /><div><br />My name is Bob Smith, but people call me Smithy. Here is my home page:<br /><a href=""></a>.<br />I live in Albuquerque, NM and work as an engineer at ACME Corp.<br />My friends:<br /><a href="">Darryl</a>,<br /><a href="">Edna</a><br /></div><br />
  39. 39. RDFa (RDF in HTML)<br /><div xmlns:v="" typeof="v:Person"><br /> My name is <span property="v:name">Bob Smith</span>,<br /> but people call me <span property="v:nickname">Smithy</span>.<br /> Here is my homepage:<br /> <a href="" rel="v:url"></a>.<br /> I live in<br /> <span rel="v:address"><br /> <span typeof="v:Address"><br /> <span property="v:locality">Albuquerque</span>,<br /> <span property="v:region">NM</span><br /> </span><br /> </span><br /> and work as an <span property="v:title">engineer</span><br /> at <span property="v:affiliation">ACME Corp</span>.<br /> My friends:<br /> <a href="" rel="v:friend">Darryl</a>,<br /> <a href="" rel="v:friend">Edna</a><br /></div><br />
  40. 40. What to publish?<br />Literal Triples<br /><> <br /> <foaf:name> <br /> “Coldplay” <br />Outgoing Links<br /><> <br /> <owl:sameAs> <br /> <><br />Incoming Link<br /><> <br /> <mo:member_of> <br /> <> <br />
  41. 41. What to publish?<br />Description of the data set<br />Semantic Sitemaps<br />voiD (Vocabulary of Interlinked Datasets)<br />Provenance Metadata<br />Licenses Information<br />
  42. 42. Vocabularies (or Schemas or Ontologies)<br />Create your own using<br />Simple Knowledge Organization Systems (SKOS)<br />Taxonomy<br />RDF Vocabulary Description Language (RDF Schema)<br />Light weight vocabularies<br />Web Ontological Language (OWL)<br />Highly expressive and capable of inferencing<br />
  43. 43. Vocabularies (or Schemas or Ontologies)<br />Reuse vocabularies<br />Dublin Core: metadata attributes<br />Friend of a Friend (FOAF): persons and relationships<br />Semantically Interlinked Online Communities (SIOC): describing users, posts, blogs, etc<br />Description of a Project (DOAP)<br />Music Ontology<br />Programmes Ontology: TV and radio programs<br />Good Relations: describing products and services<br />Review Vocabulary<br />Basic Geo (WGS84) Vocabulary<br />
  44. 44. 4) Include links to other things<br />
  45. 45. 4) Include links to other things<br />Set external RDF links into other data sources on the Web<br />Subject of the triple is in the namespace of one data set<br />Object of the triple is a URI in the namespace of another data set<br />Connect siloed data islands<br />Enable discovery<br />
  46. 46. 4) Include links to other things<br />Relationship Links<br /><><br /> <> <><br />Identity Link<br /><><br /> <><br /> <> <br />Vocabulary Links<br /><><br /> <><br /> <> <br />
  47. 47. Which predicate for linking to choose?<br />Depends on your domain<br />Is it widely used?<br />owl:sameAs<br />foaf:knows<br />foaf:based_near<br />…<br />If you create your own, relate it to a widely used predicate<br />
  48. 48. How to create the links?<br />Manually<br />Works for small and static data sets<br />I want to find another URI that identifies the same real object that I have<br />Sindice and Falcons provide index of URIs by keyword<br />(Semi) Automatic<br />Record Linkage/Identity Resolution/Co-reference<br />Silk:<br />LIMES:<br />