1. CS570 Artificial Intelligence Semantic Web & Ontology 2
Kwak Nohyun
Lee youn-ki
Hwang young-bae

2. Contents Why do we need the semantic web ? What is the semantic web?
XML
RDF
Ontology
DAML+OIL
Applications
Other issues

3. Why is the Semantic Web needed?
WWW is increasing very seriously.
There are some troubles in web search.
It is difficult to deal with many HTML documents intelligently.
We can’t extend, integrate, share information easily.
So, we need something else.

4. What can we do in Semantic Web?
Make the machine understand data in existing web
Very correct search in web
Inferences(New Information)
Intelligent software agent
Easy extension, sharing, integration of information

5. What is the Semantic Web?
"The Semantic Web is an extension of the current web in which information is given well-defined meaning, better enabling computers and people to work in cooperation." -- Tim Berners-Lee, James Hendler, Ora Lassila, The Semantic Web, Scientific American, May 2001

6. Semantic Web’s Layered Structure
Data:
XML
Resource
RDF, RDFS
Knowledge
Ontology
Inference AI
Agent

7. What is the Semantic Web?
Web for machine(not human)
Intelligent Web
An extension of current web
A network of knowledge(not information)
decentralized
Focus on the meaning(semantics)

8. XML XML : Document format for computer to read easily Markup language
Contrast to HTML, user make his/her own tag in XML and XML does not focus how to show the document, but what to mean
Provide possibility of the infinite expression
Tree structure

9. The standard Hollywood ….
XML Example
show
<show type="Movie">
<title>Fugitive, The</title>
<year>1993</year>
<aka>Auf der Flucht</aka>
<aka>Fuggitivo, Il</aka>
<review>
<nyt>
The standard Hollywood summer
movie strikes back.
</nyt>
</review>
<box_office>183,752,965</box_office>
<video_sales>72,450,220</video_sales>
</show>
title
······
review
Fugitive, The
nyt
The standard Hollywood ….

10. RDF(Resource Description Framework) Concepts
An infrastructure that enables the encoding, exchange and reuse of structured metadata
An application of XML
Impose structural constraints to provide unambiguous methods of expressing semantics
Means for publishing both human-readable and machine-processable vocabularies

11. The Design Goals of RDF A simple data model
Formal semantics and inference
URI-based vocabulary
XML-based syntax
Support use of XML schema data types

12. The RDF Data Model Basic type Subject Object Property
Resources : Any object that is uniquely identifiable by an URI(Uniform Resource Identifier)
Properties : a specific attribute used to describe a resource
Statement
Subject
Predicate
Object
Subject
Object
Property

13. The RDF Data Model Example1
Statement :
has a creation-date whose value is August 16,
(Does machine know that the creation-date of above homepage is August 16, 1999?)
RDF Statement
A subject
A predicate(property)
An object
August 16, 1999

14. The RDF Data Model Example1
August 16, 1999

15. The RDF Data Model Example1
RDF/XML :
<?xml version="1.0"?>
<rdf:RDF xmlns:rdf=" xmlns:exterms="
<rdf:Description rdf:about="
<exterms:creation-date>August 16, 1999</exterms:creation-date>
</rdf:Description>
</rdf:RDF>

16. The RDF Data Model Example2
Additional statements
has a creator whose value is John Smith.
has a language whose value is English.

17. The RDF Data Model Example2
August 16, 1999
English

18. The RDF Data Model Example2
<?xml version="1.0"?>
<rdf:RDF xmlns:rdf="
xmlns:dc="
xmlns:exterms="
<rdf:Description rdf:about="
<exterms:creation-date>August 16, 1999</exterms:creation-date>
<exterms:language>English</exterms:language>
<dc:creator rdf:resource="
</rdf:Description>
</rdf:RDF>

19. RDF Vocabulary Description Language : RDF Schema
An extension of RDF
Used to declare vocabularies
Provides the mechanisms needed to specify classes and properties
Provides a type system for RDF
Not provide a specific vocabulary of application-oriented classes

20. RDF Schema Summary classes properties rdfs:Class rdfs:Datatype
rdfs:Container
rdfs:Literal
...
properties
rdfs:subClassOf
rdfs:subPropertyOf
rdfs:domain
rdfs:range
rdfs:comment
rdfs:member
rdfs:seeAlso
...

21. RDFS example1 MiniVan Truck subClassOf subClassOf subClassOf
PassengerVehicle
Van
subClassOf
subClassOf
MotorVehicle

22. RDFS example1 The Vehicle Class Hierachy in RDF/XML
<?xml version="1.0"?>
<rdf:RDF xmlns:rdf=" xmlns:rdfs="
<rdf:Description rdf:ID="MotorVehicle">
<rdf:type rdf:resource="
</rdf:Description>
<rdf:Description rdf:ID="PassengerVehicle">
<rdfs:subClassOf rdf:resource="#MotorVehicle"/>

23. RDFS example1 <rdf:Description rdf:ID="Truck">
<rdf:type rdf:resource="
<rdfs:subClassOf rdf:resource="#MotorVehicle"/>
</rdf:Description>
<rdf:Description rdf:ID="Van">
<rdf:Description rdf:ID="MiniVan">
<rdfs:subClassOf rdf:resource="#Van"/>
<rdfs:subClassOf rdf:resource="#PassengerVehicle"/>
</rdf:RDF>

24. RDFS example1 An instance of MotorVehicle <?xml version="1.0"?>
<rdf:RDF xmlns:rdf=" xmlns:ex="
<rdf:Description rdf:ID="companyCar">
<rdf:type rdf:resource="
</rdf:Description>
</rdf:RDF>

25. Knowledge Representation
There exist same words having different meanings or different words having same meanings.
Computer can’t understand natural languages.
We need the special method for knowledge representation.

26. Ontology
Philosophy
A theory about the nature of existence
A systematic account of existence
A method for describing entities and relationships among entities
An explicit specification of a conceptualization
Means of describing semantics
A heart of the Semantic Web
The most typical kind of ontology
A taxonomy and a set of inference rules

27. Representation Language for Ontology
Based on First Order logic
Ontololingua
Loom
Frame-Logic
Based on XML(because of standardization)
SHOE(Simple HTML Ontology Extensions)
Resource Description Framework Schema Language(RDFS)
DAML(DARPA Agent Markup Language )
OIL(Ontology Inference Layer)
Ontology Web Language(OWL)

28. Why develop an ontology?
To share common understanding of the structure of information among people or software agents
To enable reuse of domain knowledge
To analyze domain knowledge

29. DAML+OIL Web Ontology Language
DAML(DARPA Agent Markup Language) + OIL(Ontology Inference Layer)
DAML+OIL => OWL
DAML or OIL is extension of RDF Schema

30. DAML+OIL Example Elemens: intersectionOf unionOf minCardinalityQ
<daml:Class rdf:about="#Person">
<rdfs:comment>every person is a man or a woman</rdfs:comment>
<daml:disjointUnionOf rdf:parseType="daml:collection">
<daml:Class rdf:about="#Man"/>
<daml:Class rdf:about="#Woman"/>
</daml:disjointUnionOf>
</daml:Class>
Elemens:
intersectionOf
unionOf
minCardinalityQ
maxCardinalityQ
...

31. Application Example

32. Other Issues

33. Reference http://www.w3.org/ http://www.w3.org/2001/sw/
Berners-Lee, T., Hendler, J. and Lassila, O., “The Semantic Web,” Scientific American, 2001
Decker,S., Melnik, S., Van Harmelen, “The Semantic Web: the roles of XML and RDF”, IEEE Internet Computing, 2000
McGuiness, D., “DAML+OIL: an ontology language for the Semantic Web,” IEEE Intelligent Systems, 2002