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Introduction session to the WOD-PD event in Vienna http://www.webofdata.info/

Introduction session to the WOD-PD event in Vienna http://www.webofdata.info/

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Web of data Web of data Presentation Transcript

    • Web of Data 101
    • Keith Alexander (Talis)
    • Yves Raimond (QMUL/BBC A&Mi)
    • WOD-PD 2008, October 22 nd , 2008
  • Outline
    • Introduction to linked data
    • 1 st hacking session
    • SPARQL
    • 2 nd hacking session
    • What's out there?
  • The Web of Data
  • The Web
    • Names (URIs)
    • Documents (HTML, XML, JSON, ...)
    • Interactions with names (HTTP)
    Names Documents HTTP GET
  • Links
  • What does it look like, now?
    • Names identify documents, e.g. HTML, XML, etc.
    • Documents are interlinked:
    <a href=” http://moustaki.org/ ” />
  • Web of documents
  • We understand...
  • We understand...
  • Machines don't...
  • Shortcomings
    • Untyped links
      • Friend?
      • City?
      • Favorite artist?
    • Opacity
      • Me?
      • That gig?
      • A pizza?
    • ”Give me bands that I listened to in the month who are making a gig next to my current location”
  • The Google way
    • Let's aggregate a massive amount of documents. By using the linkage information and statistical analysis, we can infer enough to provide a good search service.
  • Right, but...
    • Search is not everything
      • ”Give me bands that I listened to in the last month who are making a gig next to my current location”
    • Information extraction must cover:
      • Multiple domains
      • Multiple media
    • Frustrating
      • Documents often generated from database
      • Why reverse-engineer the ”view” process?
  • Silos and views
  • Solution
    • Easy, let's just build web services on top of the WS-* stack, wrapping every single possible database query
    • Just jocking :-)
  • Web of data
    • Let's get back to the Web:
      • Names (URIs)
      • Documents (HTML, XML, JSON, ...)
      • Interactions (HTTP GET/POST/PUT/DELETE)
    • Not only documents can be named !!
      • Persons, cities, bands, WOD-PD...
    • Documents can hold structured data
      • Stuff that your program can use
    • Problem solved. Session finished.
  • Web of data A web of things
  • RDF
    • RDF is the web standard for such structured data
    • RDF data model:
      • Subject (URI)
      • Property (URI)
      • Object (URI or literal)
  • RDF literals
    • Literals are just string values
    • They can have language tags associated with them
    • Or they can have a datatype associated with them
    • Or they can be plain
  • RDF example
    • http://moustaki.org/foaf.rdf#moustaki
    • http://xmlns.com/foaf/0.1/based_near
    • http://dbpedia.org/resource/London
    • http://dbpedia.org/resource/The_Clash
    • http://dbpedia.org/property/origin
    • http://dbpedia.org/resource/London
    • http://moustaki.org/foaf.rdf#moustaki
    • http://xmlns.com/foaf/0.1/interest
    • http://dbpedia.org/resource/The_Clash
  • RDF Me The Clash London
  • The nice thing about all those URIs
    • … is that you can look them up to get more information about the things they signify.
    • Even the properties and types are URIs. This means you can look them up to get more information about their semantics.
      • Web ontologies
    • You can also do handy things like retrieve the labels (rdfs:label) of the predicates, to create dynamic user interfaces.
  • Writing RDF
    • RDF is the data model
    • Different ways to serialise RDF
      • RDF/XML
      • Turtle
      • RDFa (RDF embedded in XHTML)
  • RDF/XML
    • <foaf:Person rdf:about=” http://moustaki.org/foaf.rdf#moustaki ”>
    • <foaf:knows rdf:resource=” http://sw-app.org/mic.xhtml#i ”/>
    • <foaf:interest rdf:resource=” http://dbpedia.org/resource/The_Clash ”>
    • <foaf:name>Yves Raimond</foaf:name>
    • </foaf:Person>
  • Turtle
    • < http://moustaki.org/foaf.rdf#moustaki >
    • a foaf:Person;
    • foaf:interest < http://dbpedia.org/resource/The_Clash >;
    • foaf:knows < http://sw-app.org/mic.xhtml#i >;
    • foaf:name ”Yves Raimond” .
  • Summary - Linked Data principles
    • Use URIs as names for things
    • Use HTTP URIs so that people can look up those names
    • When someone looks up a URI, provide useful RDF information
    • Include RDF statements that link to other URIs so that they can discover related things Tim Berners-Lee, 2007 http://www.w3.org/DesignIssues/LinkedData.html
  • Example
    • http://dbtune.org/jamendo/artist/5
    • RDF representation:
      • This is an artist
        • http://purl.org/ontology/mo/MusicArtist
      • It made two records
        • http://dbtune.org/jamendo/record/33
        • http://dbtune.org/jamendo/record/174
      • It is based near a place
        • http://sws.geonames.org/2991627/
    • More information about that place? GET it!
  • Tabulator demo