The document discusses the Semantic Web and linked data. It provides an overview of languages used for the Semantic Web like RDF, RDFS and OWL. It also discusses how semantic data can be integrated into documents, stored and queried, and issues around scalability. Finally, it covers browsing and visualization of linked data through techniques like faceted browsing and Fresnel lenses.

1. The Semantic Web in ActionKennissystemen, November 2009Rinke Hoekstra

2. OverviewThe Semantic WebLanguages and IntegrationStorage and QueryingLinked (Open) DataScalability issuesBrowsing and ViewingDEMOs… if there’s time …OWL in Action11/30/092

3. The Semantic Web IdeologyIdentity is everythingPartial solutions are great too!Layer cake11/30/093OWL

4. Semantic WebIntially

5. `Metadata’ for web pages

6. Since ~2006

7. `Web of Data’

8. Semantic web as data source in its own right

9. Linked Data

10. A ‘Databaseesque’ Web

11. RDF Triple stores

12. Query languages11/30/094

13. LanguagesMultiple Languages

14. RDF, RDFS and OWL

15. Multiple SyntaxesRDF/XML, Turtle (Restricted N3), NtripleFunctional Syntax, Manchester Syntax, OWL XMLRDF

16. Triples

17. Distributed

18. Always about something else

19. ... but can be about other RDF triples as well.11/30/095

20. Languages: RDF(S)/XML<rdf:RDFxmlns:rdf=“http://www.w3.org/1999/02/22-rdf-syntax-ns#”xmlns:rdfs="http://www.w3.org/TR/rdf-schema/"xmlns:owl=“http://www.w3.org/2002/07/owl#”xmlns:uva=“http://www.uva.nl/rdf#”xmlns=“http://www.uva.nl/people”> <rdf:Descriptionrdf:ID=“#radboud”> <rdf:typerdf:resource=“http://www.uva.nl/rdf#AssociateProfessor”/> <uva:name>RadboudWinkels</uva:name> <uva:teachesrdf:resource=“http://www.uva.nl/courses#ks2009”/> </rdf:Description> <uva:Courserdf:about=“http://www.uva.nl/courses#ks2009”/> <rdfs:Classrdf:about=“http://www.uva.nl/rdf#AssociateProfessor”> <rdfs:subClassOfrdf:resource=“http://www.uva.nl/rdf#StaffMember”/> </rdfs:Class><owl:ObjectPropertyrdf:about=“http://www.uva.nl/rdf#teaches”> <rdfs:domainrdf:resource=“http://www.uva.nl/rdf#Professor”/> <rdfs:rangerdf:resource=“http://www.uva.nl/rdf#Course”/> </owl:ObjectProperty></rdf:RDF>11/30/096

21. Languages: Turtle@prefix rdf:<http://www.w3.org/1999/02/22-rdf-syntax-ns#>.@prefix rdfs:<http://www.w3.org/TR/rdf-schema/>.@prefix owl:<http://www.w3.org/2002/07/owl#>.@prefix uva:<http://www.uva.nl/rdf#>.@prefix courses:<http://www.uva.nl/courses#>.@prefix :<http://www.uva.nl/people#>.uva:AssociateProfessor a rdfs:Class;rdfs:subClassOfuva:StaffMember.uva:teaches aowl:ObjectProperty;rdfs:domainuva:AssociateProfessor;rdfs:rangeuva:Course.:radboud a uva:AssociateProfessor;uva:name ”RadboudWinkels”^^xsd:string;uva:teachescourses:ks2009.courses:ks2009 a uva:Course.11/30/097

22. Languages: FS11/30/098Namespace(=<http://www.uva.nl/people#>)Namespace(owl=<http://www.w3.org/2002/07/owl#>)Namespace(uva=<http://www.uva.nl/rdf#>)Namespace(courses=<http://www.uva.nl/courses#>)Declaration(Class(uva:Course))Declaration(Class(uva:StaffMember))Declaration(Class(uva:AssociateProfessor))SubClassOf(uva:AssociateProfessoruva:StaffMember)Declaration(DataProperty(uva:name))Declaration(ObjectProperty(uva:teaches))ObjectPropertyDomain(uva:teachesuva:AssociateProfessor)ObjectPropertyRange(uva2:teaches uva:Course)Declaration(Individual(courses:ks2009))Declaration(Individual(radboud))ObjectPropertyAssertion(uva:teachesradboud courses:ks2009)DataPropertyAssertion(uva:nameradboud "RadboudWinkels")

23. IntegrationHow to add this ‘meta’ to my ‘data’?Three options:Old fashioned HTML:<link rel='meta' type='application/rdf+xml' href='http://www.leibnizcenter.org/~hoekstra/foaf.rdf' title='FOAF'> HTTP 303 `see other’http://www.w3.org/TR/swbp-vocab-pub/Inline (RDFa/GRDDL)11/30/099

24. Integration: 303 See Other (Demo)http://www.metalex.eu/metalex11/30/0910

25. Integration: Inline RDFaAttributes on XHTML elementshttp://www.w3.org/TR/xhtml-rdfa-primerGRDDLGleaning Resource Descriptions from Dialects of LanguagesExplicit reference to (XSL) transformationhttp://www.w3.org/TR/grddl/11/30/0911

26. Integration: RDFa ExampleIn XHTML:<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML+RDFa 1.0//EN" "http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd"><html xmlns:cal="http://www.w3.org/2002/12/cal/ical#"> <head><title>Jo's Friends and Family Blog</title></head> <body> <p instanceof="cal:Vevent"> I'm holding <span property="cal:summary">one last summer Barbecue</span>, on <span property="cal:dtstart" content="20070916T1600-0500"> September 16th at 4pm. </span> </p> </body></html>In RDF:_:blanknode0 rdf:type cal:Vevent; cal:summary ”one last summer Barbecue"; cal:dtstart "20070916T1600-0500" .11/30/0912

27. Integration: GRDDLIn HTML/XML instance documents:<html xmlns="http://www.w3.org/1999/xhtml" xmlns:grddl='http://www.w3.org/2003/g/data-view#' grddl:transformation="glean_title.xsl http://www.w3.org/2001/sw/grddl-wg/td/getAuthor.xsl”>In XML Schema documents: <xsd:annotation> <xsd:appinfo> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"> <rdf:Description rdf:about="http://www.metalex.eu/latest"> <grddl:namespaceTransformation rdf:resource=”http://www.metalex.eu/grddl/metalex2owl.xsl" /> </rdf:Description> </rdf:RDF> </xsd:appinfo> </xsd:annotation>11/30/0913

28. Storage (on the web)As documents.rdf, .n3, .turtle, .htmlRDF triple storesSesame, Joseki, 4Store, AllegroGraph, OpenLink Virtuoso, SDB/TDB, Open Calais, SWI Prolog Reasoners ‘on top’, or via DIGPellet, OWLIM, etc.SPARQL EndpointsResults as JSON, XML, CSV etc.11/30/0914

29. QueryingOriginally many languagesSPARQL, nRQL, SeRQL, etc. SPARQL: http://www.w3.org/TR/rdf-sparql-query/ExamplePREFIX course: <http://www.uva.nl/courses#>PREFIX uva: <http://www.uva.nl/rdf#>SELECT ?nameWHERE { ?x uva:teaches course:ks2007. ?x uva:name ?name }?x binds with <http://www.uva.nl/people#radboud> ?name binds with “Radboud Winkels”^^xsd:string11/30/0915

30. Querying (2)SPARQL 1.0select, construct, from, optional, filterNegation via unbound variableSPARQL 1.1update, negation, aggregation, subqueries 11/30/0916

31. The Web of Data… does it exist?11/30/0917

32. Linked Open Data11/30/0918

33. 11/30/0919November 2009: 13.1 Billion triples, 142 Million links

34. But there’s moreLate additions…

35. New York Times archives

36. Now 5k names, with 4 references to LOD

37. Will grow to > 30k

38. Reuters

39. OpenCalais automated tagging

40. Soon to come

41. Data.gov (via RPI)

42. Whitehouse.gov (via Drupal)

43. Data.gov.uk (directly)

44. European Parliament (MetaLex+RDFa)11/30/0920

45. ScalabilityHow to deal with massive amounts of data?Consequences for reasoningBillion Triple Challenge(864.8 Million Triples)Consequences for queryingTable lookups, joins etc.… and what about …Dealing with change, provenance, trust?11/30/0921

46. A rough idea…I can crash a DL reasoner using an ontology of ~15 classes and 5 individuals (honestly)What if my ontology contains thousands of classes and billions of individuals?11/30/0922

47. ReasoningWhen?

48. Realtime vs. in advance

49. Lightweight reasoning (RDFS, OWL 2 RL)

50. Implementable using forward chaining rules

51. Still problems with scalability

52. Distributed reasoning (DAS-3)

53. MaRVIN

54. ‘SpeedDate’ distrubution of triples across nodes

55. MapReduce

56. Full closure of BTC in 57 minutes

57. Output: 30B triples

58. And what to do with the results?11/30/0923

59. 2 Degrees from Kevin BaconPREFIX p: http://dbpedia.org/property/SELECT ?film1 ?actor1 ?film2 ?actor2WHERE { ?film1 p:starring <http://dbpedia.org/resource/Kevin_Bacon> . ?film1 p:starring ?actor1 . ?film2 p:starring ?actor1 . ?film2 p:starring ?actor2 .}11/30/0924DBPedia: 150M triples

60. Rough idea…1 Billion triples in MySQL

61. Load time

62. … a couple of hours

63. Simple table lookup (one-variable query)

64. … about 5 minutes

65. Single join (two-variable query)

66. … a couple of hours

67. Better indexes?

68. Harddisk access times are the bottleneck (9ms)

69. More targeted reasoning, querying, federation.11/30/0925

70. Let’s suppose that all worksViewing the web of data11/30/0926

71. Browsing and ViewingHow to unlock your RDF/OWL to users?Custom applications (PizzaFinder)Generic RDF Browsers (Faceted Browsing)How to present your RDF/OWL to users?Custom applications (TopBraid Geo)Generic RDF Visualisation (Fresnel Lenses)11/30/0927

72. Browsing: FacetsMulti-dimensional searchUser filters available informationContext dependentFacetUI elementValues of a propertyNumber of resultsQuery building11/30/0928

73. BrowsingMIT Longwellhttp://simile.mit.edu/longwell/demo/libraries/facethttp://slashfacet.semanticweb.orgFlamencoRDFBrowserExhibithttp://simile.mit.edu/exhibitLENAOpenAcademiahttp://vu.openacademia.org11/30/0929

74. ViewingTables are boring!Different data? Different presentation:URI/URLImagesStringsCoordinatesFiltering dataAggregating data11/30/0930

75. Viewing: FresnelRDF specification of

76. What data to present, and

77. How to present it

78. http://www.w3.org/2005/04/fresnel-info

79. Lenses

80. Group information (class membership, SPARQL result)

81. Formats

82. Specify how property values should be rendered11/30/0931

83. Viewing: Fresnel lens:foafPersonDefaultLens rdf:type fresnel:Lens ; fresnel:purpose fresnel:defaultLens ; fresnel:classLensDomain foaf:Person ; fresnel:group :foafGroup ; fresnel:showProperties ( foaf:name foaf:surname foaf:depiction ) .:knowsLens rdf:type fresnel:Lens ; fresnel:classLensDomain foaf:Person ; fresnel:group :foafGroup ; fresnel:showProperties ( foaf:name foaf:surname foaf:mbox [ rdf:type fresnel:PropertyDescription ; fresnel:property foaf:knows ; fresnel:sublens :foafPersonDefaultLens ] ) .11/30/0932

84. Viewing: Fresnel format:foafGroup rdf:type fresnel:Group ; fresnel:stylesheetLink <http://www.example.org/example.css> . :depictFormat rdf:type fresnel:Format ; fresnel:propertyFormatDomain foaf:depiction ; fresnel:label fresnel:none ; fresnel:value fresnel:image ; fresnel:valueStyle "imageWithThickBorder"^^fresnel:styleClass ; fresnel:group :foafGroup .:urlFormat rdf:type fresnel:Format ; fresnel:propertyFormatDomain foaf:homepage ; fresnel:propertyFormatDomain foaf:mbox ; fresnel:value fresnel:externalLink ; fresnel:labelStyle "basicLabel"^^fresnel:styleClass ; fresnel:valueStyle "basicUrl"^^fresnel:styleClass ; fresnel:group :foafGroup .11/30/0933

85. Longwell11/30/0934

86. /facet11/30/0935

87. Some Demos11/30/0936

88. OWL in Action11/30/0937

89. OWL in ActionWhat OWL can do…

90. Traditional

91. Straightforward classification tasks

92. Extensions

93. Explanation & Justification

94. Probabilistic Reasoning

95. Advanced (Law)

96. Temporal reasoning (Klarman et al., 2008)

97. Legal reasoning (van de Ven et al., 2008)11/30/0938

98. Legal assessmentCase input Individual case descriptionMatchCase is matched against a set of normsResolve conflictsWhere multiple norms apply, the system determines whether and which norms have priority over othersFinal verdict

99. University library regulationsNorms qualify a situation1a) Students registered at this university are allowed to check out a book from this library1b) Students registered at other universities are allowed to check out a book from this library provided that they are enrolled in at least one course given at this university.1c) Students who have checked out more than five books are not allowed to check out another book.Expected subsumption hierarchy:Art1c ⊑ Art1a, Art1c ⊑ Art1bAmy C {Amy :Student, book_1 :Library_Book, … , book_6 :Library_BookAmychecks_out book_1, … , Amychecks_out book_6}

100. Norms in LKIF Core

101. A Default Norm0) Default: Checking out books is disallowed.Default_GC ⊑ Generic_Case⊑ ∃disallowed_by.{defaultnorm}≡ ∃checks_out.Library_Book Default_Norm ⊑ Prohibition ⊑ ∀disallows.Default_GC≡ {defaultnorm}

102. Article 1a1a) Students registered at this university are allowed to check out a book from this library.Art1a_GC ⊑ Generic_Case⊑ ∃allowed_by.art1a≡ Registered_Student ⊓∃checks_out.Library_Book Art1a_Permission ⊑ Permission⊑ ∀allows.Art1a_GC≡ {art1a}

103. Article 1c1c) Students who have checked out more than five books are not allowed to check out another book.Art1c_GC_F ⊑Generic_Case⊑∃disallowed_by.{art1c}≡ Registered_Student ⊓≥ 6 checks_out.Library_BookArt1c_GC_P ⊑Generic_Case⊑∃allowed_by.{art1c}≡ Registered_Student ⊓∃checks_out.Library_Book ≤ 5 checks_out.Library_BookArt1c_Prohibition ⊑ Prohibition⊑ ∀disallows.Art1c_GC_F ⊓ ∀allows.Art1c_GC_P ≡ {art1c}

104. Judging Amy

105. Resourceshttp://www.w3.orgRDF(S), N3, OWL, SPARQL, RDFa, GRDDL, XML, XMLSchema, XSLT, CSS, XPath, fresnel...

106. http://www.semanticweb.org/facet, other resources

107. http://www.planetrdf.comAggregated RSS feed of the cool & famous

108. NEW: OWL 2

109. http://www.w3.org/TR/owl-overview11/30/0946