1. The Semantic Web in ActionKennissystemen, November 2009 Rinke Hoekstra
2. Overview The Semantic Web Languages and Integration Storage and Querying Linked (Open) Data Scalability issues Browsing and Viewing DEMOs … if there’s time … OWL in Action 11/30/09 2
3. The Semantic Web Ideology Identity is everything Partial solutions are great too! Layer cake 11/30/09 3 OWL
23. Integration How 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) 11/30/09 9
25. Integration: Inline RDFa Attributes on XHTML elements http://www.w3.org/TR/xhtml-rdfa-primer GRDDL Gleaning Resource Descriptions from Dialects of Languages Explicit reference to (XSL) transformation http://www.w3.org/TR/grddl/ 11/30/09 11
28. Storage (on the web) As documents .rdf, .n3, .turtle, .html RDF triple stores Sesame, Joseki, 4Store, AllegroGraph, OpenLink Virtuoso, SDB/TDB, Open Calais, SWI Prolog Reasoners ‘on top’, or via DIG Pellet, OWLIM, etc. SPARQL Endpoints Results as JSON, XML, CSV etc. 11/30/09 14
29. Querying Originally many languages SPARQL, nRQL, SeRQL, etc. SPARQL: http://www.w3.org/TR/rdf-sparql-query/ Example PREFIX course: <http://www.uva.nl/courses#> PREFIX uva: <http://www.uva.nl/rdf#> SELECT ?name WHERE { ?x uva:teaches course:ks2007. ?x uva:name ?name } ?x binds with <http://www.uva.nl/people#radboud> ?name binds with “Radboud Winkels”^^xsd:string 11/30/09 15
45. Scalability How to deal with massive amounts of data? Consequences for reasoning Billion Triple Challenge (864.8 Million Triples) Consequences for querying Table lookups, joins etc. … and what about … Dealing with change, provenance, trust? 11/30/09 21
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? 11/30/09 22
71. Browsing and Viewing How 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) 11/30/09 27
72. Browsing: Facets Multi-dimensional search User filters available information Context dependent Facet UI element Values of a property Number of results Query building 11/30/09 28
73. Browsing MIT Longwell http://simile.mit.edu/longwell/demo/libraries /facet http://slashfacet.semanticweb.org Flamenco RDFBrowser Exhibit http://simile.mit.edu/exhibit LENA OpenAcademia http://vu.openacademia.org 11/30/09 29
74. Viewing Tables are boring! Different data? Different presentation: URI/URL Images Strings Coordinates Filtering data Aggregating data 11/30/09 30
98. Legal assessment Case input Individual case description Match Case is matched against a set of norms Resolve conflicts Where multiple norms apply, the system determines whether and which norms have priority over others Final verdict
99. University library regulations Norms qualify a situation 1a) Students registered at this university are allowed to check out a book from this library 1b) 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 ⊑ Art1b Amy C {Amy :Student, book_1 :Library_Book, … , book_6 :Library_Book Amychecks_out book_1, … , Amychecks_out book_6}
101. A Default Norm 0) 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 1a 1a) 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 1c 1c) 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_Book Art1c_GC_P ⊑Generic_Case ⊑∃allowed_by.{art1c} ≡ Registered_Student ⊓∃checks_out.Library_Book ≤ 5 checks_out.Library_Book Art1c_Prohibition ⊑ Prohibition ⊑ ∀disallows.Art1c_GC_F ⊓ ∀allows.Art1c_GC_P ≡ {art1c}
