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The SemanticWeb in ActionKennissystemen, December 2008
Rinke Hoekstra
04/12/232
Overview
The Semantic Web Languages and Integration Storage and Querying Browsing and Viewing Mashups Reasoning (OWL in Action) ... does it really exist?
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The Semantic Web Ideology
Identity is everything Partial solutions are great too! Layer cake
OWLOWL
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Languages: RDF notations
Different ways of writing RDF RDF/XML RDF/XML Abbrev N3
Turtleonly allows valid RDF-graphs
Ntripleone triple per line, fully qualified URI’s.
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Languages: RDF(S)/XML Code Example.<rdf:RDF xmlns:rdf=“http://www.w3.org/1999/02/22-rdf-syntax-ns#” xmlns:rdfs="http://www.w3.org/TR/rdf-schema/" xmlns:uva=“http://www.uva.nl/rdf#” xmlns=“http://www.uva.nl/people”> <rdf:Description rdf:ID=“#radboud”> <rdf:type rdf:resource=“http://www.uva.nl/rdf#AssociateProfessor”/> <uva:name>Radboud Winkels</uva:name> <uva:teaches rdf:resource=“http://www.uva.nl/courses#ks2008”/> </rdf:Description> <uva:Course rdf:about=“http://www.uva.nl/courses#ks2008”/> <rdfs:Class rdf:about=“http://www.uva.nl/rdf#AssociateProfessor”> <rdfs:subClassOf rdf:resource=“http://www.uva.nl/rdf#StaffMember”/> </rdfs:Class> <rdf:Property rdf:about=“http://www.uva.nl/rdf#teaches”> <rdfs:domain rdf:resource=“http://www.uva.nl/rdf#Professor”/> <rdfs:range rdf:resource=“http://www.uva.nl/rdf#Course”/> </rdf:Property></rdf:RDF>
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Languages: Turtle@prefix rdf:<http://www.w3.org/1999/02/22-rdf-syntax-ns#>.@prefix rdfs:<http://www.w3.org/TR/rdf-schema/>.@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:subClassOf uva:StaffMember.
uva:teaches a rdf:Property;rdfs:domain uva:AssociateProfessor;rdfs:range uva:Course.
:radboud a uva:AssociateProfessor;uva:name ”Radboud Winkels”^^xsd:string;uva:teaches courses:ks2008.
courses:ks2008 a uva:Course.
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Languages: Important Message
Multiple Syntaxes! RDF statements are:
Triples <subject, predicate,object> Distributed Always about something else ... but can be about other RDF triples as
well.
Metadata
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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)
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Integration: 303 See Other (Demo)
http://www.metalex.eu/metalex
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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/
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Integration: RDFa Example
In 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" .
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Integration: GRDDL
In 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>
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Storage (on the web)
As documents .rdf, .n3, .turtle, .html
In a RDF triple-store Sesame (http://www.openrdf.org) Jena/Joseki (http://jena.sourceforge.net)
RDF(S)/OWL reasoning Jena’s OntModel Sesame OWLIM Sail module
SPARQL Endpoints Results as JSON (JavaScript Object
Notation) http://darius.leibnizcenter.org:8080/openrdf-sesame
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Querying
Many languages SPARQL, 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 ?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
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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)
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Browsing: Facets
Multi-dimensional search User filters available information Context dependent Facet
UI element Values of a property Number of results
Query building
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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
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Viewing
Tables are boring! Different data? Different presentation:
URI/URL Images Strings Coordinates
Filtering data Aggregating data
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Viewing: Fresnel
RDF specification of What data to present, and How to present it
http://www.w3.org/2005/04/fresnel-info
Lenses Group information
(class membership, SPARQL result)
Formats Specify how property values should be
rendered
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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 ] ) .
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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 .
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Longwell
04/12/2323
/facet
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Mashups
Combining arbitrary sources of data
Potluck http://simile.mit.edu/potluck
Yahoo Pipes http://pipes.yahoo.com
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Yahoo Pipes Editing
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Yahoo Pipes Result
OWL in Action
What OWL can do… Traditional
Straightforward classification tasks
Extensions Explanation & Justification Probabilistic Reasoning
Advanced (Law) Temporal reasoning (Klarman et al., 2008) Legal reasoning (van de Ven et al., 2008)
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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
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
AmyC {Amy :Student, book_1 :Library_Book, … , book_6 :Library_BookAmy checks_out book_1, … , Amy checks_out book_6}
Norms in LKIF Core
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}
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}
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_BookArt1c_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}
Judging Amy
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Million dollar question
... does the SemanticWeb really exist? Semantics: yes Web: mwoah
Friend-of-a-Friend (FOAF) RSS feeds (pingbacks etc.) Web 2.0: Tagging + Mashups
Reasoning? Local, ‘in the box’ But: MaRVIN (http://www.larkc.eu/marvin/)
However The nuts ‘n bolts are ready, And we’ve got the data!
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Resources
http://www.w3.orgRDF(S), N3, OWL, SPARQL, RDFa, GRDDL, XML, XMLSchema, XSLT, CSS, XPath, fresnel...
http://www.semanticweb.org/facet, other resources
http://www.planetrdf.comAggregated RSS feed of the cool & famous
NEW: OWL 2 http://www.w3.org/2007/OWL/
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