Linked  data and rdf
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Linked data and rdf

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Linked  data and rdf Linked data and rdf Presentation Transcript

  • Linked Data and RDF Semantic Engineering Seminar WS 2013/14 Daniel Nüst daniel.nuest@wwu.de
  • Linked Data WWW > Web of Documents CSV, XML, HTML tables >>> Web of Data Typed Links, to & from >>> global data graph LOD
  • Principles 1. Use URIs to denote things. 2. Use HTTP URIs [#, /] so that these things can be referred to and looked up ("dereferenced") by people and user agents. 3. Provide useful information [metadata (aliases, DC terms, technical: means of access, formats)] about the thing when its URI is dereferenced, leveraging standards such as RDF, SPARQL. 4. Include links to other [!] related things (using their URIs) when publishing data on the Web [reusing vocabularies]. http://en.wikipedia.org/wiki/Linked_data
  • 2.46 billion pieces of information (RDF triples) http://lod-cloud.net/ http://dbpedia.org/
  • http://lov.okfn.org/dataset/lov/index.html
  • http://lov.okfn.org/dataset/lov/details/vocabulary_geo.html
  • RDF (.rdf) “HTML for data” the thing the value the property Goals/Applications transfer information between machines (not people) without loss of meaning, “identified on the web” Vocabularies (terms) for statements Serializations http://www.w3.org/TR/rdf-primer/ <Subject> <Predicate> <Object>
  • http://www.w3.org/TR/rdf-primer/ http://www.example.org/index.html has a creator whose value is John Smith
  • http://www.example.org/index.html has a creator whose value is John Smith http://www.w3.org/TR/rdf-primer/ http://www.example.org/index.html has a creation-date whose value is August 16, 1999 http://www.example.org/index.html has a language whose value is English
  • <http://www.example.org/index.html> <http://purl.org/dc/elements/1.1/creator> <http://www.example.org/staffid/8574 <http://www.example.org/index.html> <http://www.example.org/terms/creation-date> "August 16, 1999" . <http://www.example.org/index.html> <http://purl.org/dc/elements/1.1/language> "en" . (shared) Vocabularies namespace URI: http://www.example.org/ convention ex:index.html dc:creator exstaff:85740 . ex:index.html exterms:creation-date "August 16, 1999" . ex:index.html dc:language "en" . fy:joefy.iunm ed:dsfbups fytubgg:85740 . http://www.w3.org/TR/rdf-primer/ prefix ex: prefix dc: namespace URI: http://purl.org/dc/elements/1.1/ prefix exterms: namespace URI: http://www.example.org/terms/ prefix exstaff: namespace URI: http://www.example.org/staffid/
  • John Smith has a an age whose value is 27 <http://www.example.org/staffid/85740> <http://www.example.org/terms/age> "27"^^<http://www.w3.org/2001/XMLSchema#integer> . ex:index.html exterms:creation-date "1999-08-16"^^xsd:date . http://www.w3.org/TR/rdf-primer/ exstaff:85740 exterms:age "27"^^xsd:integer .
  • Concepts Things you should have heard about … Data types Expression of simple facts Entailment [Literals, URIrefs, RDF/XML, graphs] http://www.w3.org/TR/rdf-concepts Blank nodes
  • http://www.w3.org/TR/rdf-primer/
  • http://www.w3.org/TR/rdf-primer/ RDF/XML
  • Turtle (.ttl) @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>. @prefix contact: <http://www.w3.org/2000/10/swap/pim/contact#>. <http://www.w3.org/People/EM/contact#me> rdf:type contact:Person; contact:fullName "Eric Miller"; contact:mailbox <mailto:em@w3.org>; contact:personalTitle "Dr.". http://www.w3.org/2007/02/turtle/primer/
  • <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdfsyntax-ns#" xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#"> <geo:Point> <geo:lat>55.701</geo:lat> <geo:long>12.552</geo:long> </geo:Point> </rdf:RDF> http://www.w3.org/2003/01/geo/#example Geo and RDF
  • <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#" xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns="http://xmlns.com/foaf/0.1/"> <Person> <name>Dan Brickley</name> <homepage dc:title="Dan's home page" rdf:resource="http://danbri.org/"/> <based_near geo:lat="51.47026" geo:long="2.59466"/> <rdfs:seeAlso rdf:resource="http:/danbri.org/foaf.rdf"/> <!-- more RDF here, using any RDF vocabularies --> </Person> </rdf:RDF> http://www.w3.org/2003/01/geo/#example Geo, FOAF & DC
  • Resources and references > see handout! THANKS!
  • Linked data applications browsers – navigate/traverse data sources using links/RDF triples (connecting web of {documents, data}) search engines – start of the navigation human-oriented (like Google…) application-oriented (reuse indexing for different apps) domain applications Dbpedia Mobile, Revyu, DERI pipes, …
  • RDFa 1.0 Example http://en.wikipedia.org/wiki/RDFa
  • RDFs and OWL RDF Schema > http://en.wikipedia.org/wiki/RDF_Schema Web Ontology Language > http://en.wikipedia.org/wiki/Web_Ontology_Language more expressive See also https://www.cambridgesemantics.com/de/semantic-university/rdfs-vs.-owl