1. Creating Linked Data Juan F. Sequeda Semantic Technology Conference June 2011

2. Linked Data is a set of best practices to publish and interlink data on the web

3. Linked Data Principles 1.Use URIs as names for things 2.Use HTTP URIs so that people can look up (dereference) those names. 3.When someone looks up a URI, provide useful information. 4.Include links to other URIs so that they can discover more things.

4. 1) Use URIs as names for things

5. 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

6. 1) Use URIs as names for things http://juansequeda.com/foaf.rdf#mehttp://www.w3.org/People/Berners-Lee/card#i http://xmlns.com/foaf/0.1/knows

7. 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

8. 2) Use HTTP URIs so that people can look up (dereference) those names.

9. 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

10. Dereference a URI?

16. What’s with the redirection?

28. RDFa … The trouble with Bob Alice …. …

30. 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 webserver http://mycompany.comhttp://mycompany.com I now can mint URIs in this namespace: – http://mycompany.com/person/Juan-Sequeda http://mycompany.com/person/Juan-Sequeda

31. Create Cool URIs If you don’t control a namespace, don’t misuse it – http://www.imdb.com/title http://www.imdb.com/title Avoid implementation details – http://foo.mycompany.com:8080/person.php?id= 123&format=rdf 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/Juan-Sequeda – http://mycompany.com/person/123 http://mycompany.com/person/123

32. 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

33. 3) Provide useful information

34. 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

35. RDF subject – predicate – object Coldplay is the artist of Viva la Vida http://dbpedia.org/resource/Coldplay http://dbpedia.org/resource/Viva_la_Vida http://dbpedia.org/ontology/artist

36. prefix dbpedia-owl: prefix foaf: prefix dbprop: prefix geo: http://dbpedia.org/resource/Coldplay http://dbpedia.org/resource/Viva_la_Vida http://dbpedia.org/resource/London dbpedia-owl:artistfoaf:name dbprop:origin geo:longgeo:lat “Coldplay” 51.507778 -0.128056

37. . <dbpedia-owl:Band xmlns:dbpedia-owl="http://dbpedia.org/ontology/" rdf:about="http://dbpedia.org/resource/Coldplay"> @prefix rdf:. a ;. ntriples RDF/XML turtle

38. HTML My name is Bob Smith, but people call me Smithy. Here is my home page: www.example.com. I live in Albuquerque, NM and work as an engineer at ACME Corp. My friends: Darryl, Edna

39. RDFa (RDF in HTML) My name is Bob Smith, but people call me Smithy. Here is my homepage: www.example.com. I live in Albuquerque, NM and work as an engineer at ACME Corp. My friends: Darryl, Edna

40. What to publish? Literal Triples “Coldplay” Outgoing Links Incoming Link

41. What to publish? Description of the data set – Semantic Sitemaps – voiD (Vocabulary of Interlinked Datasets) Provenance Metadata Licenses Information

42. 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

43. 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

44. 4) Include links to other things

45. 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

46. 4) Include links to other things Relationship Links Identity Link Vocabulary Links

47. 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

48. 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