An inference engine for
the semantic web
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Naudts Guido |
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Student at the Open University |
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Netherlands |
Case study
The layers of the
semantic web
SGML and HTML
XML Properties
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Meta-language |
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Subset of SGML |
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Definition of tags –standardisation? |
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Hierarchical |
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Namespaces = mix of languages! |
XML Example
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<?xml version="1.0 ?> |
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<!DOCTYPE book SYSTEM "http://somesite.org/book.dtd"> |
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<book id="nielsen01"> |
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<title> |
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Designing Web Usability |
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</title> |
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<info> |
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<key> |
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Design |
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</key> |
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<key> |
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Internet |
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</key> |
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<isbn> |
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1-56205-810-X |
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</isbn> |
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</info> |
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</book> |
DTD Example
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<!DOCTYPE book |
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[ <!ELEMENT book (title, subtitle?, author+, info) > |
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<!ATTLIST book id CDATA
#REQUIRED > |
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<!ELEMENT title PCDATA > |
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<!ELEMENT subtitle PCDATA > |
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<!ELEMENT author PCDATA > |
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<!ELEMENT info (key*, isbn) > |
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<!ELEMENT key PCDATA > |
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<!ELEMENT isbn
PCDATA > |
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]> |
XML Schema example
The layers of the
semantic web
Basics of RDF
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Anything can be a resource. |
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Resources have URIs. |
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Resources have properties. |
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Properties have values and types. |
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An RDF document makes statements about
resources and their properties. |
RDF Properties
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RDF is a language ==> |
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syntax and semantics |
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XML syntax |
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Notation 3 syntax |
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A Simple Example
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“Jan Hanford created the J.S. Bach
homepage.” |
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The J.S. Bach homepage is a resource |
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It has a URI (http://www.jsbach.org) |
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It has a property |
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The property has a type of “creator” |
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The property has a value of “Jan
Hanford” |
RDF Graph
Translated to
(simplified) RDF:
Namespaces added:
RDF Schema
RDF Schema example
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<!-- $Id: animal.rdf,v 1.2
2001/10/01 00:12:34 amdus Exp $ --> |
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<!-- A simple RDF file for parser testing --> |
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<rdf:RDF |
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xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" |
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xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" |
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xmlns:daml="http://www.daml.org/2001/03/daml+oil#" |
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xmlns="http://www.daml.org/2000/12/daml+oil#"> |
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<rdfs:Class rdf:ID="Animal"> |
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<rdfs:label>Animal</rdfs:label> |
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<restrictedBy> |
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<Restriction> |
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<onProperty rdf:resource="#parent"/> |
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<cardinality>2</cardinality> |
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</Restriction> |
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</restrictedBy> |
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</rdfs:Class> |
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</rdf:RDF> |
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The layers of the
semantic web
Ontology
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Terms used to describe an area of
knowledge |
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Classes, relationships, properties,
subclasses |
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Definition of semantics |
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Avoid tower of Babel |
The layers of the
semantic web
Closed world assumption
Open world assumption
The layers of the
semantic web
Proof
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Proof validation, not generation |
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Simple things: a èb, a thus b. |
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validation: do the URI’s exist, are the steps followed in the
reasoning valid? |
The layers of the
semantic web
Trust
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Build a web of trust |
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Truth = trust I believe x |
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Absolute truth ==> a pinguin is a
bird |
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Contradictions between trusted parties? |
Structure of the project
Thesis questions 1
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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 ? |
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can meta-logical frameworks be used to
specify the inference engine of the semantic web? |
Thesis questions 2
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what optimisation techniques can be used? |
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how can inconsistencies best be
avoided? |
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which
system of logic should be followed on the internet? |
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what is the interpretation of the logic
i.e. what are its semantics? |
Metalogical frameworks
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Logic + methodology used to represent
other logics and to reason about their metalogical properties |
Optimisation and
consistency
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Reorder clauses |
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Limit the search space |
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Detect inconsistencies i.e. logic
contradiction; might be violation of constraints |
N3 example part 1
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# $Id: authen.axiom.n3,v 1.2 2001/10/01
00:12:34 amdus Exp $ |
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@prefix log:
<http://www.w3.org/2000/10/swap/log#>. |
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@prefix : <authen#>. |
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<mailto:jos.deroo.jd@belgium.agfa.com>
:member <http://www.agfa.com>. |
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<http://www.agfa.com> :w3cmember
<http://www.w3.org>. |
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<http://www.agfa.com> :subscribed
<mailto:w3c-ac-forum@w3.org/>. |
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{{:person :member :institution. |
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:institution :w3cmember <http://www.w3.org>. |
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:institution :subscribed :mailinglist} log:implies |
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{:person :authenticated :mailinglist}}
a log:Truth; log:forAll :person, :mailinglist, :institution. |
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N3 example part 2
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# $Id: authen.lemma.n3,v 1.3 2001/10/15
22:40:11 amdus Exp $ |
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@prefix log:
<http://www.w3.org/2000/10/swap/log#>. |
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@prefix : <authen#>. |
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_:who :authenticated
<mailto:w3c-ac-forum@w3.org/>. |
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N3 example part 3
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# Generated with
http://www.agfa.com/w3c/euler/#28.061 on Sat Dec 01 02:19:27 GMT+01:00 2001 |
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# for query
http://www.agfa.com/w3c/euler/authen.lemma.n3 |
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# given
[http://www.agfa.com/w3c/euler/authen.axiom.n3] |
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@prefix log:
<http://www.w3.org/2000/10/swap/log#>. |
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@prefix :
<http://www.agfa.com/w3c/euler/authen#>. |
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{<mailto:jos.deroo.jd@belgium.agfa.com> :member
<http://www.agfa.com>. |
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<http://www.agfa.com> :w3cmember <http://www.w3.org>. |
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<http://www.agfa.com> :subscribed
<mailto:w3c-ac-forum@w3.org/>} log:implies |
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{<mailto:jos.deroo.jd@belgium.agfa.com>
:authenticated <mailto:w3c-ac-forum@w3.org/>}. |
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# Proof found for
http://www.agfa.com/w3c/euler/authen.lemma.n3 in 3 steps (232 steps/sec) |
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