An inference engine for the

steelsquareInternet and Web Development

Oct 20, 2013 (3 years and 11 months ago)

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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 book

SYSTEM

"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


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.

Basics of RDF

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RDF Properties


RDF is a language ==>


syntax and semantics


XML syntax


Notation 3 syntax


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”

RDF Graph

http://www.jsbach.org

Jan Hanford

has the creator

Resource

Property Type

Property Value

Translated to (simplified) RDF:

<RDF>


<Description about="
http://www.jsbach.org
">



<
Creator
>
Jan Hanford
</Creator>


</Description>

</RDF>


Resource

Property
Value

Property
Type

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

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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


慮sw敲e= 湯n!! B散慵獥 潦 捬潳敤
w潲汤o慳獵浰瑩潮⸠



22

Open world assumption


Case study:


I have a list of important internet sites; site A is on my list


獩s攠A⁩猠業灯牴慮t.



Site B is not on my list


獩瑥 䈠楳潴i業灯牴慮a㼿?



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

戬b愠瑨畳a戮



validation: do the URI’s exist, are the
steps followed in the reasoning
valid?

25

The layers of the semantic web

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Trust


Build a web of trust


Truth = trust I believe x


Absolute truth ==> a pinguin is a bird


Contradictions between trusted
parties?

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Structure of the project

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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?

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Metalogical frameworks


Logic + methodology used to
represent other logics and to reason
about their metalogical properties

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Optimisation and consistency


Reorder clauses


Limit the search space


Detect inconsistencies i.e. logic
contradiction; might be violation of
constraints

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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)