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