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An inference engine for the semantic web

An inference engine for the semantic web. Naudts Guido Student at the Open University Netherlands. Case study. The layers of the semantic web. SGML and HTML. SGML and HTML HTML is an application of SGML. An application is a set of SGML tags and attribute .

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An inference engine for the semantic web

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  1. An inference engine for the semantic web Naudts Guido Student at the Open University Netherlands

  2. Case study

  3. The layers of the semantic web

  4. SGML and HTML SGML and HTML HTML is an application of SGML. An application is a set of SGML tags and attribute . The tags are used for the presentation of the document. Here's a simple HTML document: <html> <head> <title> My home page </title> </head> <body> <h1>Hello there!</h1> <p> <font color="blue">Welcome to my home page!</font> </p> </body> </html>

  5. XML Properties • Meta-language • Subset of SGML • Definition of tags –standardisation? • Hierarchical • Namespaces = mix of languages!

  6. XML Example <?xml version="1.0 ?> <!DOCTYPE bookSYSTEM"http://somesite.org/book.dtd"> <book id="nielsen01"> <title> Designing Web Usability </title> <info> <key> Design </key> <key> Internet </key> <isbn> 1-56205-810-X </isbn>  </info> </book>

  7. DTD Example <!DOCTYPE book [ <!ELEMENT book (title, subtitle?, author+, info) > <!ATTLIST book id CDATA #REQUIRED > <!ELEMENT title PCDATA > <!ELEMENT subtitle PCDATA > <!ELEMENT author PCDATA > <!ELEMENT info (key*, isbn) > <!ELEMENT key PCDATA > <!ELEMENT isbn PCDATA > ]>

  8. XML Schema example

  9. The layers of the semantic web

  10. Basics of RDF • Anything can be a resource. • Resources have URIs. • Resources have properties. • Properties have values and types. • An RDF document makes statements about resources and their properties.

  11. RDF Properties • RDF is a language ==> syntax and semantics • XML syntax • Notation 3 syntax

  12. A Simple Example • “Jan Hanford created the J.S. Bach homepage.” • The J.S. Bach homepage is a resource • It has a URI (http://www.jsbach.org) • It has a property • The property has a type of “creator” • The property has a value of “Jan Hanford”

  13. http://www.jsbach.org Jan Hanford RDF Graph Property Type Property Value Resource has the creator

  14. Translated to (simplified) RDF: Resource <RDF> <Description about="http://www.jsbach.org"> <Creator>Jan Hanford</Creator> </Description> </RDF> Property Value Property Type

  15. Namespaces added: <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/DC/"> <rdf:Description about="http://www.jsbach.org/"> <dc:Creator>Jan Hanford</dc:Creator> </rdf:Description> </rdf:RDF>

  16. RDF Schema

  17. RDF Schema example <!-- $Id: animal.rdf,v 1.2 2001/10/01 00:12:34 amdus Exp $ --> <!-- A simple RDF file for parser testing --> <rdf:RDF xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:daml="http://www.daml.org/2001/03/daml+oil#" xmlns="http://www.daml.org/2000/12/daml+oil#"> <rdfs:Class rdf:ID="Animal"> <rdfs:label>Animal</rdfs:label> <restrictedBy> <Restriction> <onProperty rdf:resource="#parent"/> <cardinality>2</cardinality> </Restriction> </restrictedBy> </rdfs:Class> </rdf:RDF>

  18. The layers of the semantic web

  19. Ontology • Terms used to describe an area of knowledge • Classes, relationships, properties, subclasses • Definition of semantics • Avoid tower of Babel

  20. The layers of the semantic web

  21. Closed world assumption • Case study: Jos is member of W3C. All members of W3C are entitled to recieve W3C-mail. Therefore Jos is entitled to recieve W3C-mail. We pose the query: Can Jim recieve mail from the W3C? Jim is not in the list  answer = no!!! Because of closed world assumption.

  22. Open world assumption • Case study: I have a list of important internet sites; site A is on my list  site A is important. Site B is not on my list  site B is not important??? Conclusion : Open World is de default assumption, Closed World must be enforced.

  23. The layers of the semantic web

  24. Proof • Proof validation, not generation • Simple things: a b, a thus b. • validation: do the URI’s exist, are the steps followed in the reasoning valid?

  25. The layers of the semantic web

  26. Trust • Build a web of trust • Truth = trust I believe x • Absolute truth ==> a pinguin is a bird • Contradictions between trusted parties?

  27. Structure of the project

  28. Thesis questions 1 • What is the best way for realising an inference engine so that the restrictions that are imposed by the structure of the World Wide Web on the Semantic Web are met ? • can meta-logical frameworks be used to specify the inference engine of the semantic web?

  29. Thesis questions 2 • what optimisation techniques can be used? • how can inconsistencies best be avoided? • which system of logic should be followed on the internet? • what is the interpretation of the logic i.e. what are its semantics?

  30. Metalogical frameworks • Logic + methodology used to represent other logics and to reason about their metalogical properties

  31. Optimisation and consistency • Reorder clauses • Limit the search space • Detect inconsistencies i.e. logic contradiction; might be violation of constraints

  32. N3 example part 1 • # $Id: authen.axiom.n3,v 1.2 2001/10/01 00:12:34 amdus Exp $ • @prefix log: <http://www.w3.org/2000/10/swap/log#>. • @prefix : <authen#>. • <mailto:jos.deroo.jd@belgium.agfa.com> :member <http://www.agfa.com>. • <http://www.agfa.com> :w3cmember <http://www.w3.org>. • <http://www.agfa.com> :subscribed <mailto:w3c-ac-forum@w3.org/>. • {{:person :member :institution. • :institution :w3cmember <http://www.w3.org>. • :institution :subscribed :mailinglist} log:implies • {:person :authenticated :mailinglist}} a log:Truth; log:forAll :person, :mailinglist, :institution.

  33. N3 example part 2 • # $Id: authen.lemma.n3,v 1.3 2001/10/15 22:40:11 amdus Exp $ • @prefix log: <http://www.w3.org/2000/10/swap/log#>. • @prefix : <authen#>. • _:who :authenticated <mailto:w3c-ac-forum@w3.org/>.

  34. N3 example part 3 • # Generated with http://www.agfa.com/w3c/euler/#28.061 on Sat Dec 01 02:19:27 GMT+01:00 2001 • # for query http://www.agfa.com/w3c/euler/authen.lemma.n3 • # given [http://www.agfa.com/w3c/euler/authen.axiom.n3] • @prefix log: <http://www.w3.org/2000/10/swap/log#>. • @prefix : <http://www.agfa.com/w3c/euler/authen#>. • {<mailto:jos.deroo.jd@belgium.agfa.com> :member <http://www.agfa.com>. • <http://www.agfa.com> :w3cmember <http://www.w3.org>. • <http://www.agfa.com> :subscribed <mailto:w3c-ac-forum@w3.org/>} log:implies • {<mailto:jos.deroo.jd@belgium.agfa.com> :authenticated <mailto:w3c-ac-forum@w3.org/>}. • # Proof found for http://www.agfa.com/w3c/euler/authen.lemma.n3 in 3 steps (232 steps/sec)

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