Upload
milton-stevens
View
221
Download
2
Embed Size (px)
Citation preview
Semantic Web and Its ApplicationsSemantic Web and Its Applications
Ching-Long Yeh 葉慶隆Department of Computer Science and Engineering
Tatung UniversityTaipei, Taiwan
Email: [email protected]://www.cse.ttu.edu.tw/chingyeh
SW & Applications 4
InformationPool
WWWWWW
HTTP (Hyper Text Transport Protocol)HTML (Hyper Text Markup Language)URL (Uniform Resource Locator)
Web server
ApplicationClient
HTTP
URL
HTML Document
• Human-to-machine interaction• Information explosion
SW & Applications 5
InformationPool
Interaction Using XML
XML (eXtensible Markup Language)SOAP (Simple Object Access Protocol)
SOAP server
Application
HTTP
XML Document
• Machine-to-machine interaction • Service automation
SOAP server
Application
InformationPool
XML Document
SW & Applications 6
Web Service Architecture
Serviceregistry
Servicerequester
Serviceprovider
FindWSDL, UDDI
PublishWSDL, UDDI
Bind
Servicedescriptions
Servicedescriptions
Services
SW & Applications 7
Electronic Business
Transport, routing, packaging
Business processes,business documents
Company ACompany B
Transport, routing, packaging
Business processes,business documents
ERPERP
• Application-to-Application• Business Process Automation• RosettaNet• ebXML
SW & Applications 8
Semantic WebSemantic Web
• The Semantic Web is a vision:
• See “W3C Semantic Web Activity,” by Marja-Riitta Koivunen, for more descriptions.
the idea of having data on the web defined and linked in a way that it can be used by machines not just for display purposes, but for automation, integration and reuse of data across various applications
SW & Applications 9
Semantic WebSemantic Web
• The Semantic Web is the new generation of the World Wide Web, based on the semantic network knowledge representation formalism, which enables packaging information in the form of object-attribute-value statements, so called triples.
• By assuming that terms used in these statements are based on the formally specified meaning (for the community of interest), i.e. ontologies, these triplets can be semantically processed by machine agents.
From: http://www2002.org/CDROM/poster/130.pdf
SW & Applications 10
The Semantic Web Layered ArchitectureThe Semantic Web Layered Architecture
(http://www.w3.org/2001/Talks/0228-tbl/slide5-0.html)
Tim Berners-Lee:“Axioms, Architecture and Aspirations”W3C all-working group plenary Meeting28 February 2001
URI Unicode
XML Namespaces
XML Schema
Sig
RDF M&S
RDF Schema
Ontology
Rules
Logic
Proof
Trust
SW & Applications 11
A Metadata Layer View of the SWA Metadata Layer View of the SW
Resources on the WWW
Metadata layer upon the WWWSchema in OWLInstances in RDF
SW & Applications 13
What is XML?What is XML?
• Extensible Markup Language• A Syntax for Documents • A Meta-Markup Language• A Structural and Semantic Language, not a Formatting
Language• Not just for Web pages
SW & Applications 14
XML StandardsXML Standards
• DTD• Namespace• Schema• DOM• CSS, XSL-T, XSL-FO• XLink• XPointer
SW & Applications 16
RDF M&SRDF M&S• RDF (Resource Description Framework)
– Beyond Machine readable to Machine understandable
• RDF consists of two parts– RDF Model (a set of triples)– RDF Syntax (different XML serialization syntaxes)
• RDF Schema for definition of Vocabularies (simple Ontologies) for RDF (and in RDF)
SW & Applications 17
RDF Data ModelRDF Data Model• Resources
– A resource is a thing you talk about (can reference)– Resources have URI’s– RDF definitions are themselves Resources (linkage, see
requirement 1)
• Properties – slots, define relationships to other resources or atomic values
• Statements– “Resource has Property with Value”– (Values can be resources or atomic XML data)
• Similar to Frame Systems
SW & Applications 18
A Simple ExampleA Simple Example• Statement
– “Ora Lassila is the creator of the resource http://www.w3.org/Home/Lassila”
• Structure– Resource (subject) http://www.w3.org/Home/Lassila– Property (predicate) http://www.schema.org/#Creator– Value (object) "Ora Lassila”
• Directed graph
http://www.w3.org/Home/Lassilas:Creator
Ora Lassila
SW & Applications 19
EmailName
s:Creator
http://www.w3.org/Home/Lassila
Another ExampleAnother Example
• To add properties to Creator, point through an intermediate Resource.
Person://fi/654645635
Ora Lassila [email protected]
SW & Applications 20
Example:Example: Bag Bag
• The students incourse 6.001 are Amy, Tim,John, Mary,and Sue
Rdf:Bag
/Students/Amy
/Students/Tim
/Students/John
/Students/Mary
/Students/Sue
bagid1
/courses/6.001
students
rdf:type
rdf:_1
rdf:_2
rdf:_3
rdf:_4
rdf:_5
SW & Applications 21
rdf:_1
rdf:_2
rdf:_3
rdf:typesource
ftp.eu.net
ftp.cs.purdue.edu
ftp.x.org
Example:Example: Alternative Alternative
• The source code for X11 may be found at ftp.x.org, ftp.cs.purdue.edu, or ftp.eu.net
altid
rdf:Althttp://x.org/package/X11
SW & Applications 22
RDF Schema (RDFS)RDF Schema (RDFS)
• RDF just defines the data model
• Need for definition of vocabularies for the data model - an
Ontology Language!
• The RDF Schema mechanism provides a basic type system for
use in RDF models.
• The RDF schema specification language is less expressive, but
much simpler to implement, than full predicate calculus languages
such as CycL and KIF.
SW & Applications 23
Most Important Modeling PrimitivesMost Important Modeling Primitives
• Core Classes– Root-Class rdfs:Resource
– MetaClass rdfs:Class
– Literals rdfs:Literal
• rdfs:subclassOf-property
• Inherited from RDF: properties (slots)
• rdfs:domain & rdfs:range
• rdfs:label, rdfs:comment, etc.
• Inherited from RDF: InstanceOf (rdf:type)
SW & Applications 24
OWLOWLW3C Web Ontology LanguageW3C Web Ontology Language
• OWL provides three increasingly expressive sublanguages: OWL Lite, OWL DL, and OWL Full.
SW & Applications 25
OWLOWLW3C Web Ontology LanguageW3C Web Ontology Language
OWL Lite language constructs
RDF Schema Features: Class rdf:Property rdfs:subClassOf rdfs:subPropertyOf rdfs:domain rdfs:range Individual
(In)Equality: equivalentClass equivalentProperty sameAs differentFrom allDifferent
Property Characteristics: inverseOf TransitiveProperty SymmetricProperty FunctionalProperty InverseFunctionalProperty
Property Type Restrictions: allValuesFrom someValuesFrom
Restricted Cardinality: minCardinality (only 0 or 1) maxCardinality (only 0 or 1) cardinality (only 0 or 1)
Header Information: ontology imports
SW & Applications 27
Uses Cases of Web OntologiesUses Cases of Web Ontologies
• Web portal • Multimedia collections • Corporate web site management • Design documentation • Agents and services • Ubiquitous computing
SW & Applications 28
An Architecture of An Architecture of Semantic Community Web Portals
(From: http://www9.org/w9cdrom/134/134.html)
SesameSesame
A generic Architecture for Storing and Querying RDF and RDF SchemaA generic Architecture for Storing and Querying RDF and RDF Schema
SW & Applications 30
What is Sesame ?What is Sesame ?
Sesame is RDF Schema-based repository
and querying facility that offers:– persistent storage of RDF data
– export of repository contents in RDF format
– data administration functionality
– query engine (RQL , SeRQL)
SW & Applications 32
The RQL Query ModuleThe RQL Query Module• The Query Module follows the path when handling a query.
SW & Applications 33
The Admin ModuleThe Admin Module
• Two main functions :– Incrementally adding RDF data/schema information.– Clearing a repository.
• The Parser delivers the information to the admin module on a per-statement basis : (S , P , O) .
• The admin subsequently checks each statement for consistency with the information already present in the repository , and infers implied information if necessary , as follow:
SW & Applications 34
The Admin Module(2)The Admin Module(2)
• If P equals type , then the admin infers that O must be a class.
• If P equals subClassOf , then the admin infers that both S and O are classes.
• If P equals subPropertyOf , then admin infers that both S and O are properties.
• If P equals domain or range , the admin infers that S must be a property and O must be a class.
SW & Applications 35
The RDF Export ModuleThe RDF Export Module
• Exports data in RDF format- Output contains actual contents of repository, query engine
outputs query results
SW & Applications 36
RQL (RDF Query Language)RQL (RDF Query Language)
• Based on OQL (standard QL for object-relational DBMS)– Set of core queries
• Class, Property, subClassOf, …– Filters
• Select-from-where– Boolean expressions– Functional composition of queries
• Path expressions– For navigating the RDF model– Allowing bridging between RDF data and schema information
SW & Applications 38
KA2KA2
• Knowledge Annotation Initiative of the Knowledge Acquisition Community
• The basic scenario– WWW documents of the KS community were annotated
according to the schema of an ontology.– The annotations enable intelligent access to these
documents and infer implicit knowledge from explicitly stated facts and rules from the ontology.
The KA2 OntologyThe KA2 Ontology
Class hierarchyPerson Employee Academic-Staff Lecturer Researcher Administrative-Staff Secretary Technical-Staff Student Phd-Student
RelationsAddress, Affiliation, Cooperates-With, Editor-Of,Email, First-Name, Has-Publication, Head-Of-Group, Head-Of-Project, Last-Name, Member-Of-Organization, Member-Of-Program-Committee, Member-Of-Research-Group, Middle-Initial, Organizer-Of-Chair-Of, Person-Name, Photo, Research-Interest, Secretary-Of, Studies-At, Supervises, Supervisor, Works-At-Project
Person-ontologyClass hierarchyOn-Line-PublicationPublication Article Article-In-Book Conference-Paper Journal-Article Technical-Report Workshop-Paper Book Journal IEEE-Expert IJHCS Special-Issue
RelationsAbstract, Book-Editor, Conference-Proceedings-Title, Contains-Article-In-Book, Contains-Article-In-Journal, Describes-Project, First-Page, Has-Author, Has-Publisher, In-Book, In-Conference, In-Journal, In-Organization,In-Workshop, Journal-Editor, Journal-Number, Journal-Publisher, Journal-Year, Last-Page, On-Line-Version, …
Publication-ontology
SW & Applications 40
Accessing the Community Web PortalAccessing the Community Web Portal
• Query capability– In F-Logic mechanism
• Navigating capability– As the easy-to-use front-end of the query mechanism
SW & Applications 43
Providing InformationProviding Information
• Integrating various syntactic and semantic formats based on the common ontology
• Three different modes of information provision are supported– Metadata-based information– Wrapper-based information– Fact-based information