Creating Linked Data 2/5 Semtech2011
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    Creating Linked Data 2/5 Semtech2011 Creating Linked Data 2/5 Semtech2011 Presentation Transcript

    • Creating Linked Data
      Juan F. Sequeda
      Semantic Technology Conference
      June 2011
    • Linked Data is a set of best practices to publish and interlink data on the web
    • Linked Data Principles
      Use URIs as names for things
      Use HTTP URIs so that people can look up (dereference) those names.
      When someone looks up a URI, provide useful information.
      Include links to other URIs so that they can discover more things.
    • 1) Use URIs as names for things
    • 1) Use URIs as names for things
      Uniform Resource Identifiers identify real world objects and abstract concepts
      Not only web documents and digital content
      People, places, locations, my car
      Know somebody, from somewhere
    • 1) Use URIs as names for things
      http://juansequeda.com/foaf.rdf#me
      http://www.w3.org/People/Berners-Lee/card#i
      http://xmlns.com/foaf/0.1/knows
    • 1) Use URIs as names for things
      http://juansequeda.com/foaf.rdf#me
      Identifies the person
      http://juansequeda.com/foaf.rdf
      Identifies an RDF document
    • 2) Use HTTP URIs so that people can look up (dereference) those names.
    • 2) Use HTTP URIs so that people can look up (dereference) those names.
      HTTP protocol is the Web’s universal access mechanism
      Linked Data only uses HTTP URIs
      URI: unique name
      HTTP URI: universal means of access to the URI
      HTTP URIs should be dereferencable
    • Dereference a URI?
    • What’s with the redirection?
    • RDFa
      <html>

      <div xmlns:dc=“http://purl.org/dc/elements/1.1/”>
      <h2 property=“dc:title”>The trouble with Bob</h2>
      <h3 property=“dc:creator”>Alice</h3>
      ….
      </div>

      </html>
    • Minting HTTP URIs
      If you own the domain name and run a web server at that location, mint URIs in this namespace
      I own the domain mycompany.com
      I run a webserverhttp://mycompany.com
      I now can mint URIs in this namespace:
      http://mycompany.com/person/Juan-Sequeda
    • Create Cool URIs
      If you don’t control a namespace, don’t misuse it
      http://www.imdb.com/title
      Avoid implementation details
      http://foo.mycompany.com:8080/person.php?id=123&format=rdf
      Use Natural Keys within URI
      http://mycompany.com/person/Juan-Sequeda
      http://mycompany.com/person/123
    • Three different URIs
      URI for the real world object (non-information resource)
      http://dbpedia.org/resource/London
      http://id.mycompany.com/person/Juan-Sequeda
      http://mycompany.com/person/Juan-Sequeda
      http://www.juansequeda.com/foaf.rdf#me
      URI for the HTML document (information resource) that describes the real world object
      http://dbpedia.org/page/London
      http://pages.mycompany.com/person/Juan-Sequeda
      http://mycompany.com/person/Juan-Sequeda.html
      URI for the RDF document (information resource) that describes the real world object
      http://dbpedia.org/data/London
      http://data.mycompany.com/Juan-Sequeda
      http://mycompany.com/person/Juan-Sequeda.rdf
      http://www.juansequeda.com/foaf.rdf
    • 3) Provide useful information
    • 3) Provide useful information
      How do we provide useful information in document form on the web?  HTML
      How do we provide useful information in data form on the web  RDF
      Different ways of serializing RDF
      RDF/XML
      RDFa
      N3
      turtle
    • RDF
      subject – predicate – object
      Coldplay is the artist of Viva la Vida
      Coldplay is the artist of Viva la Vida
      http://dbpedia.org/resource/Coldplay
      http://dbpedia.org/ontology/artist
      http://dbpedia.org/resource/Viva_la_Vida
    • prefix dbpedia-owl: <http://dbpedia.org/ontology/>
      prefix foaf: <http://xmlns.com/foaf/0.1/>
      prefix dbprop: <http://dbpedia.org/property/>
      prefix geo: <http://www.w3.org/2003/01/geo/wgs84_pos#>
      51.507778
      -0.128056
      geo:long
      geo:lat
      http://dbpedia.org/resource/London
      dbprop:origin
      http://dbpedia.org/resource/Coldplay
      dbpedia-owl:artist
      foaf:name
      http://dbpedia.org/resource/Viva_la_Vida
      “Coldplay”
    • ntriples
      <http://dbpedia.org/resource/Coldplay> <http://dbpedia.org/ontology/artist> <http://dbpedia.org/resource/Viva_la_Vida> .
      <http://dbpedia.org/resource/Coldplay> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://dbpedia.org/ontology/Band> .
      RDF/XML
      <?xml version="1.0" encoding="utf-8"?>
      <rdf:RDFxmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
      <dbpedia-owl:Bandxmlns:dbpedia-owl="http://dbpedia.org/ontology/"
      rdf:about="http://dbpedia.org/resource/Coldplay">
      <dbpedia-owl:artistrdf:resource="http://dbpedia.org/resource/Viva_la_Vida"/> </dbpedia-owl:Band>
      </rdf:RDF>
      turtle
      @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
      <http://dbpedia.org/resource/Coldplay>
      a <http://dbpedia.org/ontology/Band> ;
      <http://dbpedia.org/ontology/artist> <http://dbpedia.org/resource/Viva_la_Vida> .
    • HTML
      <div>
      My name is Bob Smith, but people call me Smithy. Here is my home page:
      <a href="http://www.example.com">www.example.com</a>.
      I live in Albuquerque, NM and work as an engineer at ACME Corp.
      My friends:
      <a href="http://darryl-blog.example.com">Darryl</a>,
      <a href="http://edna-blog.example.com">Edna</a>
      </div>
    • RDFa (RDF in HTML)
      <div xmlns:v="http://rdf.data-vocabulary.org/#" typeof="v:Person">
      My name is <span property="v:name">Bob Smith</span>,
      but people call me <span property="v:nickname">Smithy</span>.
      Here is my homepage:
      <a href="http://www.example.com" rel="v:url">www.example.com</a>.
      I live in
      <span rel="v:address">
      <span typeof="v:Address">
      <span property="v:locality">Albuquerque</span>,
      <span property="v:region">NM</span>
      </span>
      </span>
      and work as an <span property="v:title">engineer</span>
      at <span property="v:affiliation">ACME Corp</span>.
      My friends:
      <a href="http://darryl-blog.example.com" rel="v:friend">Darryl</a>,
      <a href="http://edna-blog.example.com" rel="v:friend">Edna</a>
      </div>
    • What to publish?
      Literal Triples
      <http://www.bbc.co.uk/music/artists/cc197bad-dc9c-440d-a5b5-d52ba2e14234#artist>
      <foaf:name>
      “Coldplay”
      Outgoing Links
      <http://www.bbc.co.uk/music/artists/cc197bad-dc9c-440d-a5b5-d52ba2e14234#artist>
      <owl:sameAs>
      <http://dbpedia.org/resource/Coldplay>
      Incoming Link
      <http://www.bbc.co.uk/music/artists/18690715-59fa-4e4d-bcf3-8025cf1c23e0#artist>
      <mo:member_of>
      <http://www.bbc.co.uk/music/artists/cc197bad-dc9c-440d-a5b5-d52ba2e14234#artist>
    • What to publish?
      Description of the data set
      Semantic Sitemaps
      voiD (Vocabulary of Interlinked Datasets)
      Provenance Metadata
      Licenses Information
    • Vocabularies (or Schemas or Ontologies)
      Create your own using
      Simple Knowledge Organization Systems (SKOS)
      Taxonomy
      RDF Vocabulary Description Language (RDF Schema)
      Light weight vocabularies
      Web Ontological Language (OWL)
      Highly expressive and capable of inferencing
    • Vocabularies (or Schemas or Ontologies)
      Reuse vocabularies
      Dublin Core: metadata attributes
      Friend of a Friend (FOAF): persons and relationships
      Semantically Interlinked Online Communities (SIOC): describing users, posts, blogs, etc
      Description of a Project (DOAP)
      Music Ontology
      Programmes Ontology: TV and radio programs
      Good Relations: describing products and services
      Review Vocabulary
      Basic Geo (WGS84) Vocabulary
    • 4) Include links to other things
    • 4) Include links to other things
      Set external RDF links into other data sources on the Web
      Subject of the triple is in the namespace of one data set
      Object of the triple is a URI in the namespace of another data set
      Connect siloed data islands
      Enable discovery
    • 4) Include links to other things
      Relationship Links
      <http://www.bbc.co.uk/music/artists/cc197bad-dc9c-440d-a5b5-d52ba2e14234#artist>
      <http://xmlns.com/foaf/0.1/based_near> <http://dbpedia.org/resource/London>
      Identity Link
      <http://www.bbc.co.uk/music/artists/cc197bad-dc9c-440d-a5b5-d52ba2e14234#artist>
      <http://www.w3.org/2002/07/owl#sameAs>
      <http://dbpedia.org/resource/Coldplay>
      Vocabulary Links
      <http://purl.org/ontology/mo/image>
      <http://www.w3.org/2000/01/rdf-schema#subPropertyOf>
      <http://xmlns.com/foaf/0.1/depiction>
    • Which predicate for linking to choose?
      Depends on your domain
      Is it widely used?
      owl:sameAs
      foaf:knows
      foaf:based_near

      If you create your own, relate it to a widely used predicate
    • How to create the links?
      Manually
      Works for small and static data sets
      I want to find another URI that identifies the same real object that I have
      Sindice and Falcons provide index of URIs by keyword
      (Semi) Automatic
      Record Linkage/Identity Resolution/Co-reference
      Silk: http://www4.wiwiss.fu-berlin.de/bizer/silk/
      LIMES: http://aksw.org/Projects/limes