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Semantic Web Portal. Ching-Long Yeh 葉慶隆 Department of Computer Science and Engineering Tatung University [email protected] http://www.cse.ttu.edu.tw/chingyeh. Outline. A brief description to the Semantic Web Portal Architectural basis of the Semantic Web

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semantic web portal

Semantic Web Portal

Ching-Long Yeh 葉慶隆

Department of Computer Science and Engineering

Tatung University

[email protected]

http://www.cse.ttu.edu.tw/chingyeh

outline
Outline
  • A brief description to the Semantic Web Portal
  • Architectural basis of the Semantic Web
  • KA2: an ontology-based web portal
  • An architecture of RDF triple data store
  • Conclusions

Semantic Web Portal

introduction to semantic web
Introduction to Semantic Web
  • Facilities to put machine-understandable data on the Web are becoming a high priority for many communities.
  • The Web can reach its full potential only if it becomes a place where data can be shared and processed by automated tools as well as by people.
  • For the Web to scale, tomorrow\'s programs must be able to share and process data even when these programs have been designed totally independently.

Semantic Web Portal

introduction to semantic web1
Introduction to Semantic Web
  • The Semantic Web is a vision:

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

  • See “W3C Semantic Web Activity,” by Marja-Riitta Koivunen, for more descriptions.

Semantic Web Portal

the semantic web layered architecture
The Semantic Web Layered Architecture

Trust

Proof

Sig

Tim Berners-Lee:

“Axioms, Architecture and Aspirations”

W3C all-working group plenary Meeting

28 February 2001

Logic

Rules

Ontology

RDF Schema

(http://www.w3.org/2001/Talks/0228-tbl/slide5-0.html)

RDF M&S

XML Schema

XML

Namespaces

URI

Unicode

Semantic Web Portal

ai s chance
Increasing demand for formalized knowledge on the Web: AI’s chance!

XML- & RDF-based markup languages provide a \'universal\' storage/interchange format for such Web-distributed knowledge representation.

AI’s Chance

Namespaces

CSS

DTDs

XSLT

DAML

Stylesheets

Agents

Transformations

Ontobroker

XQL

XML

HornML

Rules

Queries

XQuery

RuleML

XML-QL

SHOE

RDF[S]

Frames

Acquisition

TopicMaps

Protégé

Semantic Web Portal

web portals
Web Portals
  • A web portal is a web site that provides information content on a common topic.
    • General portals, e.g., Yahoo, Excite, Netscape, Lycos, CNET, MSN, and AOL.com
    • Specialized portal e.g., gardeners.com, semanticweb.org
  • Making valuable information to be found
    • directory service,
    • search facility
    • news, e-mail,
    • community forum

Semantic Web Portal

what is a portal
What is a portal?
  • In it\'s simplest form a portal is a filter for web content - a place from which users can locate all the Web resources that they commonly need.
  • Good portals are very successful at building online communities by bringing like-minded people together in one place.
  • As these communities are created, portal owners strive to offer a broader range of additional services in an attempt to hold on to their audiences for as long as possible.

Semantic Web Portal

what is a subject portal
What is a Subject Portal?
  • A Subject Portal could also be described as a \'vertical portal\'.
  • Rather than a gateway to all Web content, a subject portal presents a tailored view of the Web within a common subject area.
  • From an academic perspective, the desire for detail and depth is far too great and the desired information far too hidden, for conventional portal services to satisfy these communities.

Semantic Web Portal

ontology based web portals
Ontology-Based Web Portals
  • Ontology represents
    • common knowledge and interests sharing within their community
  • Tasks that ontology can be used to support a portal
    • Accessing a portal
      • Conceptual search and navigation
      • Inference capabilities
    • Providing information
      • Methods and tools accounting for the diversity of information sources

Semantic Web Portal

introduction to xml based ontology

Trust

Proof

Sig

Logic

Rules

Ontology

RDF Schema

RDF M&S

XML Schema

XML

Namespaces

URI

Unicode

Introduction to XML-Based Ontology

Semantic Web Portal

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

Semantic Web Portal

namespace bindings
Namespace Bindings
  • Prefixes are bound to namespace URIs by attaching an xmlns:prefix attribute to the prefixed element or one of its ancestors, prefix:name1 ,...,prefix:namen
  • The value of the xmlns:prefix attribute is a URI, which may or (unlike for DTDs!) may not point to a description of the namespace’s syntax
  • An element can use bindings for multiple name-spaces via attributes xmlns:prefix1 ,...,xmlns:prefixm

Semantic Web Portal

xml document instance and dtd
XML Document Instance and DTD

<mail:address xmlns:mail="http://www.deutschepost.de/"

xmlns:tele="http://www.telekom.de/">

<mail:name>Xaver M. Linde</mail:name>

<mail:street>Wikingerufer 7</mail:street>

<mail:town>10555 Berlin</mail:town>

<mail:bill>12.50</mail:bill>

<tele:phone>030/1234567</tele:phone>

<tele:phone>030/1234568</tele:phone>

<tele:fax>030/1234569</tele:fax>

<tele:bill>76.20</tele:bill>

</ mail:address>

<!ELEMENT address (name, street, town,

bill, phone+, fax+, bill)>

<!ELEMENT name (#PCDATA)>

<!ELEMENT street (#PCDATA)>

<!ELEMENT town (#PCDATA)>

<!ELEMENT bill (#PCDATA)>

<!ELEMENT phone (#PCDATA)>

<!ELEMENT fax (#PCDATA)>

<!ELEMENT ARTIST (#PCDATA)>

Semantic Web Portal

xml schema
XML Schema
  • An XML syntax that\'s an alternative and/or supplement to DTDs
  • Data typing of element and attribute content

Semantic Web Portal

rdf m s
RDF 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)
rdf data model
RDF 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

Semantic Web Portal

a simple example

Ora Lassila

A 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

s:Creator

http://www.w3.org/Home/Lassila

Semantic Web Portal

another example
Another Example
  • To add properties to Creator, point through an intermediate Resource.

http://www.w3.org/Home/Lassila

s:Creator

Person://fi/654645635

Name

Email

Ora Lassila

[email protected]

Semantic Web Portal

example bag

/courses/6.001

Example: Bag
  • The students incourse 6.001 are Amy, Tim,John, Mary,and Sue

Rdf:Bag

rdf:type

/Students/Amy

students

rdf:_1

rdf:_2

/Students/Tim

bagid1

rdf:_3

/Students/John

rdf:_4

/Students/Mary

rdf:_5

/Students/Sue

Semantic Web Portal

example alternative
Example: Alternative
  • The source code for X11 may be found at ftp.x.org, ftp.cs.purdue.edu, or ftp.eu.net

http://x.org/package/X11

rdf:Alt

rdf:type

source

altid

rdf:_1

ftp.x.org

rdf:_2

ftp.cs.purdue.edu

rdf:_3

ftp.eu.net

Semantic Web Portal

rdf syntax i
RDF Syntax I
  • Data model does not enforce particular syntax
  • Specification suggests many different syntaxes based on XML
  • General form:

Subject (OID)

Starts an RDF-Description

<rdf:RDF>

<rdf:Description about="http://www.w3.org/Home/Lassila">

<s:Creator>Ora Lassila</s:Creator>

<s:createdWith rdf:resource=“http://www.w3c.org/amaya”/>

</rdf:Description>

</rdf:RDF>

Literal

Resource (possibly another RDF-description)

Properties

Semantic Web Portal

resulting graph
Resulting Graph

http://www.w3.org/Home/Lassila

s:createdWith

s:Creator

http://www.w3c.org/amaya

Ora Lassila

<rdf:RDF>

<rdf:Description about="http://www.w3.org/Home/Lassila">

<s:Creator>Ora Lassila</s:Creator>

<s:createdWith rdf:resource=“http://www.w3c.org/amaya”/>

</rdf:Description>

</rdf:RDF>

Semantic Web Portal

rdf syntax ii syntactic varieties
RDF Syntax II: Syntactic Varieties

Typing Information

Subject (OID)

In-Element Property

<s:Homepage rdf:about="http://www.w3.org/Home/Lassila”

s:Creator=“Ora Lassila”/>

<s:createdWith>

<s:HTMLEditor rdf:about=“http://www.w3c.org/amaya”/>

</s:createdWith>

</s:Homepage>

rdf:type

s:Homepage

http://www.w3.org/Home/Lassila

Property

s:createdWith

s:Creator

rdf:type

HTMLEditor

http://www.w3c.org/amaya

Ora Lassila

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.

Semantic Web Portal

most important modeling primitives
Most 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)

Semantic Web Portal

daml oil an ontology language
DAML+OIL: an Ontology Language
  • Extension of RDF Schema
  • Ontology Language DAML+OIL: Result of a Joint (European + US-American) Committee
  • Extension of RDF Schema
    • Class Expressions (Intersection, Union, Complement)
    • XML Schema Datatypes
    • Enumerations
    • Property Restrictions
      • Cardinality Constraints
      • Value Restrictions

Semantic Web Portal

example intersection synonyms
Example: Intersection & Synonyms

<daml:Class rdf:ID="TallMan">

<daml:intersectionOf rdf:parseType="daml:collection">

<daml:Class rdf:about="#TallThing"/>

<daml:Class rdf:about="#Man"/>

</daml:intersectionOf>

</daml:Class>

<daml:Class rdf:ID="HumanBeing">

<daml:sameClassAs rdf:resource="#Person"/>

</daml:Class>

Semantic Web Portal

example disjoint complement
Example: Disjoint & Complement

<daml:Disjoint rdf:parseType="daml:collection">

<daml:Class rdf:about="#Car"/>

<daml:Class rdf:about="#Person"/>

<daml:Class rdf:about="#Plant"/>

</daml:Disjoint>

Disjoint not strictly necessary, since expressible via pairwise subClassOf

of complementOf, as for Car and Person:

<daml:Class rdf:ID="Car">

<rdfs:comment>no car is a person</rdfs:comment>

<rdfs:subClassOf>

<daml:Class>

<daml:complementOf rdf:resource="#Person"/>

</daml:Class>

</rdfs:subClassOf>

</daml:Class>

Semantic Web Portal

example properties transitive inverse subproperty uniqueproperty range datatypes
Example: Properties (Transitive, Inverse, subProperty, UniqueProperty, range, Datatypes)

<daml:TransitiveProperty rdf:ID="hasAncestor"/>

<daml:ObjectProperty rdf:ID="hasChild">

<daml:inverseOf rdf:resource="#hasParent"/>

</daml:ObjectProperty>

<daml:UniqueProperty rdf:ID="hasMother">

<rdfs:subPropertyOf rdf:resource="#hasParent"/>

<rdfs:range rdf:resource="#Female"/>

</daml:UniqueProperty>

<daml:DatatypeProperty rdf:ID="age">

<rdf:type rdf:resource="http://www.daml.org/2001/03/daml+oil#UniqueProperty"/>

<rdfs:range rdf:resource="http://www.w3.org/.../XMLSchema#nonNegativeInteger"/>

</daml:DatatypeProperty>

Semantic Web Portal

using user defined datatypes based on xml schema
Using User-defined Datatypes(based on XML Schema)

<xsd:simpleType name="over17">

<!--over17 is an XMLS datatype based on decimal-->

<!--with the added restriction that values must be >=18-->

<xsd:restriction base="xsd:decimal">

<xsd:minInclusive value="18"/>

</xsd:restriction>

</xsd:simpleType>

<daml:Class rdf:ID="Adult">

<daml:intersectionOf rdf:parseType="daml:collection">

<daml:Class rdf:about="#Person"/>

<daml:Restriction>

<daml:onProperty rdf:resource="#age"/>

<daml:hasClass rdf:resource="somefile#over17"/>

</daml:Restriction>

</daml:intersectionOf>

</daml:Class>

Semantic Web Portal

instances individuals
Instances (Individuals)

<daml:Class rdf:ID="Person">

. . .

</daml:Class>

<Person rdf:ID="Adam">

<rdfs:label>Adam</rdfs:label>

<rdfs:comment>Adam is a person.</rdfs:comment>

<age><xsd:integer rdf:value="13"/></age>

<shoesize>

<xsd:decimal rdf:value="9.5"/>

</shoesize>

</Person>

Semantic Web Portal

web services
Web Services

Semantic Web Portal

daml s
DAML-S
  • Users and software agents should be able to discover, invoke, compose, and monitor Web resources offering particular services and having particular properties.
  • As part of the DARPA Agent Markup Language program, we have begun to develop an ontology of services, called DAML-S.

Semantic Web Portal

top level of the service ontology
Top Level of the Service Ontology

Resource

provides

ServiceProfile

presents

(what it does)

Service

(how it works)

(how to access it)

supports

described by

ServiceGrounding

ServiceModel

Semantic Web Portal

process modeling ontology
Process Modeling Ontology

Semantic Web Portal

slide39

Business Process

Specification

in XML

Semantic Web Portal

slide41
KA2
  • 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.

Semantic Web Portal

the ka2 ontology
The KA2 Ontology

Person-ontology

Publication-ontology

Class hierarchy

Person

Employee

Academic-Staff

Lecturer

Researcher

Administrative-Staff

Secretary

Technical-Staff

Student

Phd-Student

Relations

Address, 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

Class hierarchy

On-Line-Publication

Publication

Article

Article-In-Book

Conference-Paper

Journal-Article

Technical-Report

Workshop-Paper

Book

Journal

IEEE-Expert

IJHCS

Special-Issue

Relations

Abstract, 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, …

accessing the community web portal
Accessing the Community Web Portal
  • Query capability
    • In F-Logic mechanism
  • Navigating capability
    • As the easy-to-use front-end of the query mechanism

Semantic Web Portal

query capabilities
Query Capabilities

FORALL Pub <-

EXISTS ResID ResID:Researcher[NAME->> Steffen "Staab";

PUBLICATION ->> Pub].

For all publications of the researcher “Steffen Staab”.

Two researchers cooperate,

if a Researcher X works at a Project Proj and

if a Researcher Y works at the same Project Proj and

X is another person than Y

FORALL X; Y; Proj

X:Researcher[COOPERATESWITH ->> Y:Researcher]

<-

X:Researcher[WORKSATPROJECT->>Proj:Project]

AND

Y:Researcher[WORKSATPROJECT->>Proj:Project]

AND NOT equal(X; Y ):

Which researchers are cooperating with other r?

FORALL ResID1, ResID2 <-

ResID1:Researcher[COOPERATESWITH ->> ResID2].

Semantic Web Portal

navigating and querying the portal
Navigating and Querying the Portal
  • Query the portal using F-Logic is too inconvenient.
  • Navigating and querying the web
    • A hypertext link may contain a query dynamically evaluated when clicking on the link (See P. 45)
    • Query generated by using the hyperbolic view interface (See P. 46)
    • Queries may be personalized and for the different users and available for the user in a selection list.
    • An expert mode: Querying the portal by typing an F-Logic statement

Semantic Web Portal

providing information
Providing 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

Semantic Web Portal

metadata based information
Metadata-based Information

In RDF, XML

Metadata

Information

source

Annotation tool

(OntoPad Annotea, …)

Semantic Web Portal

wrapper based information
Wrapper-based Information
  • Annotating information sources by hand is time-consuming.

Semi-structured

Information sources

(e.g., HTML)

Wrapper

program

Metadata

Structured

Information sources

(e.g., RDB)

(Onto Wrapper)

Semantic Web Portal

fact based information
Fact-Based Information

create

New facts

add,

modify,

delete

Knowledge

warehouse

Fact Editor

(Ontoedit, OilED,

Protégé 2000)

Semantic Web Portal

development of web portals
Development of Web Portals

Semantic Web Portal

the system architecture
The System Architecture

Semantic Web Portal

rdf parser and generator
RDF Parser and Generator
  • Using DCG in Prolog as the development tool
  • Formal grammar in RDF M&S Spec http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/#grammar

Formal grammar

rules in DCG

Prolog’s

working storage

Prolog’s

inference engine

User

interface

Semantic Web Portal

slide56

[6.1] RDF ::= [\'<rdf:RDF>\'] obj* [\'</rdf:RDF>\']

[6.2] obj ::= description | container

[6.3] description ::= \'<rdf:Description\' idAboutAttr? bagIdAttr? propAttr* \'/>\'

| \'<rdf:Description\' idAboutAttr? bagIdAttr? propAttr* \'>\'

propertyElt* \'</rdf:Description>\'

| typedNode

[6.4] container ::= sequence | bag | alternative

rdf(Objs) -->

([\'<?\'],

([nm/\'xml\'];[nm/\'XML\'];

[nm/\'xmls\'];[nm/\'XMLS\']),

([nm/\'version\',\'=\',qs/_];[]),

([nm/\'encoding\',\'=\',qs/_];[]),

[\'?>\'],{wl(\'XML heading\')}

;[]),

(fullSTG(\'RDF\',NS)

;

halfSTG(\'RDF\',NS),

[\'>\']

;

[ ]),

objStar(Objs),

(fullETG(\'RDF\',NS);[ ]).

objStar(Out) -->

obj(O),

objStar(R),{Out=[O|R]}

;

[],{Out=[]}.

obj(Obj) -->

container(Obj)

; description(_),{getAllTriples(Obj)}.

getAllTriples(Obj):- findall(statement(A,B,C),statement(A,B,C),Obj).

description(_) -->

halfSTG(\'Description\',NS),

(idAboutAttr(IdAboutAttr);[]),

(bagIdAttr(BagIdAttr);[]),

propAttrStar(IdAboutAttr),

([\'/>\']

;

[\'>\'],

propertyEltStar(IdAboutAttr),

fullETG(\'Description\',NS)), {reificationOfStatements(IdAboutAttr,BagIdAttr)}

;

typedNode.

slide57

<rdf:RDF

xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"

xmlns:dc="http://purl.org/metadata/dublin_core#">

<rdf:Description about="http://www.foo.com/cool.html">

<dc:Creator>

<rdf:Seq ID="CreatorsAlphabeticalBySurname">

<rdf:li>Mary Andrew</rdf:li>

<rdf:li>Jacky Crystal</rdf:li>

</rdf:Seq>

</dc:Creator>

<dc:Identifier>

<rdf:Bag ID="MirroredSites">

<rdf:li rdf:resource="http://www.foo.com.au/cool.html"/>

<rdf:li rdf:resource="http://www.foo.com.it/cool.html"/>

</rdf:Bag>

</dc:Identifier>

<dc:Title>

<rdf:Alt>

<rdf:li xml:lang="en">The Coolest Web Page</rdf:li>

<rdf:li xml:lang="it">Il Pagio di Web Fuba</rdf:li>

</rdf:Alt>

</dc:Title></rdf:Description></rdf:RDF>

RDF input

[statement(about/http://www.foo.com/cool.html,

Title,

alt(_87882,[string/The Coolest Web Page,

string/Il Pagio di Web Fuba])),

statement(about/http://www.foo.com/cool.html,

Identifier,

bag(id/MirroredSites,[resource/http://www.foo.com.au/cool.html,

resource/http://www.foo.com.it/cool.html])),

statement(about/http://www.foo.com/cool.html,

Creator,

seq(id/CreatorsAlphabeticalBySurname,[string/Mary Andrew,

string/Jacky Crystal]))]

Prolog

output

rdf statements in rdb tables
RDF Statements in RDB Tables

RDF_NameSpace

RDF_Resource

RDF_Statement

RDF_Predicate

RDF_Literal

user interface conceptual search
User InterfaceConceptual Search
  • Natural language interface is the best choice, but is very difficult to obtain a good result.
  • Form-based interface is easy to implement, but is too restricted.
  • Hierarchical directory browsing is perhaps a good idea, if the domain in question is well organized.
  • We also propose a frame-based query interface.

target_concept[(attribute1[:value1], …)]

teacher(office:6th_floor)

Semantic Web Portal

user interface natural language generation
User InterfaceNatural Language Generation

Knowledge

Warehouse

(RDF)

Content

extraction

Text

planning

Multi-sentential

text

Content

planning

NLG

Semantic Web Portal

future work
Future Work
  • Building an ontology for the Digital Archive Services
    • Consisting of resource and process parts
  • Declarative approach to semantic web service
    • Using an workflow engine to interpret the process descriptions
  • Intelligent Q&A for digital archive

Semantic Web Portal

summary
Summary
  • Semantic Web portals
    • Machine-understandable information
    • RDF store
    • Accessing information
      • Navigation and query
    • Providing information
      • Annotation, wrapper, fact editing
    • Enabling automatic processing by software agents

Semantic Web Portal

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