Semantic Web
Web as a communication infrastructure between humanand machines

Hideaki Takeda
National Institute of Informatics
takeda＠nii.ac.jp
Hideaki Takeda / National Institute of

Layers for Information Cycle
Internetl Web
l Semantic Web
l Linked Datal Social Networkl

Share

Collect

PublishUse&Linked Data

CreateSocial Network

RDF/RDFS/OWL

Semantic Web

URI/HTML/HTTP

Web

TCP/IPInternet
Hideaki Takeda / National Institute ofOutline
What is Semantic Web?
n XML
l Realization of Semantic Web
n Metadatan Dublin Coren RDFn RDF Scheman OWLlHideaki Takeda / National Institute of

The Aim of The Semantic Webl

"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."
The Semantic Web, Scientific American, May 2001, Tim Berners-Lee, James Hendler and Ora Lassilal

The Semantic Web is a vision: the idea of having data on theweb defined and linked in a way that it can be used bymachines not just for display purposes, but for automation,
integration and reuse of data across various applications.
http://www.w3.org/2001/sw/

Hideaki Takeda / National Institute ofSemantic Webl

Realization of various information exchanging via Web

Automation
自動化
Integration
統合

Re-use of data
データの再利用

Hideaki Takeda / National Institute ofNext Generation Web?
lEvolution of Web
n HTML: Web for Display
n XML: Web with Syntaxn ?? : Web with Semanticsl

Why should we embed semantics into Web?
Fromn Web for HumanTon Web for human and machines
cf. Web for machines
Hideaki Takeda / National Institute ofA brief introduction of XMLl

Limitation of HTMLn Chaos by mixture of displaying and text structuresu e.g.,
l <h3></h3> should be used for “the third-level heading”, but are often
used just for bigger fontsl <b></b> is specifying “bold” , not “emphasis”.
n Fixed Structure
u e.g.,
l If you need <h7></h7>….
l I need a structure just for my data<h1> A list of lectures</h1><h2> Knowledge Sharing Systems</h2><h3> Lecturer： Hideaki Takeda</h3><h3>Wednesday 3rd</h3>
Hideaki Takeda / National Institute ofXMLlXML(eXtensible Markup Language)n Can define original tags
n Represent logical structures of datau DTDn Do not include style information
u XST<lecturelist><lecture><title id=1234> Knowledge Sharing Systems</title><lecturer> Hideaki Takeda</lecturer><schedule><week>Wednesday</week><time>3rd</time></lecture>...
</lecturelist>
Hideaki Takeda / National Institute ofXMLlXML(eXtensible Markup Language)n A standard by W3C(The World
Wide Web Consortium ) (1998)n A subset of SGMLn Featuresu Fixed character set
u DTD is not mandatoryu Should not omit end-tags
u Style can be specifiedlSGML(Standard Generalized MarkupLanguage）
n ISO8879 (1986)
n Featuresu Can specify character setu DTD is mandatoryu Can omit end-tags
u Style can be specified

Hideaki Takeda / National Institute ofDTDlDTD(Document Type Definition):n Specify elements and attributes for XML logical structures
u Defining a specific markup languagel XHTMLu Logical structure can be specified
n Should share DTD between document authors and users<!DOCTYPE lecturelist [<!ELEMENT lecturelist (lecture*)><!ELEMENT lecture (title, lecturer*, schedule)><!ELEMENT title (#PCDATA)><!ATTLIST title id ID #REQUIRED ><!ELEMENT lecturer (#PCDATA)><!ELEMENT schedule (week, time)><!ELEMENT week (#PCDATA)><!ELEMENT time (#PCDATA)>]>
Hideaki Takeda / National Institute ofDTDlElement type declaration!"#$#%#&'()*)+),-.,/+)(0)*)+),-.12,-),-3(4n Element namen Element contentu Data typeu Childrenu Orderu Number of appearance: *(0-), +(1-, ?(0-1)

lll

Attribute-list declaration!"5''$67'()*)+),-.,/+)(/--89:;-).,/+)(/--89:;-).-<=)(>)?/;*-.@/*;)4#,-9-<(>)1*/8/-92,!"#&'6'A(),-9-<.,/+)(“B-89,C(-2(:)(8)=*/1)>D4&2-/-92,(>)1*/8/-92,(Hideaki Takeda / National Institute ofStyle SheetlXSLT（eXtensible Stylesheet Language Transformations）
n A language to describe rules to translate structures in XML
n Originally a part of XML (eXtensible Stylesheet Language )which is a language to display or print XML datan Procedureu A template for each node in the source treeu Specify which node should be applied to a template withmatch attribute of xsl:template elementu XSLT processor analyzes from the top-most node to downu Find a pattern of appearance of elements and attributes whichis specified with match attribute of xsl:template elementu Apply a rule of a template applied
Hideaki Takeda / National Institute of<?xml version="1.0" encoding="shift_jis"?><xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"><xsl:output method="html" encoding="shift_jis"/><xsl:template match="/"><html><body><xsl:apply-templates/></body></html></xsl:template><xsl:template match="lecturelist"><table border="1"><tr><td>Lecture name</td><td>Lecturer</td><td>Time</td></tr><xsl:apply-templates /></table></xsl:template><xsl:template match="lecture"><tr><xsl:apply-templates/></tr></xsl:template><xsl:template match="schedule"><xsl:template match="title"><td> <xsl:apply-templates /> </td><td><xsl:value-of select="." /></td></xsl:template></xsl:template><xsl:template match="week"><xsl:template match="lecturer"><xsl:value-of select="." />/<td><xsl:value-of select="." /></td></xsl:template></xsl:template><xsl:template match="time"><xsl:value-of select="." /></xsl:template> </xsl:stylesheet>
Hideaki Takeda / National Institute of<?xml version="1.0" encoding="shift_jis"?><?xml-stylesheet href="lecturelist.xsl" type="text/xsl" ?><!DOCTYPE lecturelist [<!ELEMENT lecturelist (lecture*)><!ELEMENT lecture (title, lecturer*, schedule)><!ELEMENT title (#PCDATA)><!ELEMENT lecturer (#PCDATA)><!ELEMENT schedule (week, time)><!ELEMENT week (#PCDATA)><!ELEMENT time (#PCDATA)>]><lecturelist><lecture><title id=1234> Knowledge Sharing
Systems</title><lecturer> Hideaki Takeda</lecturer><schedule><week>Wednesday</week><time>3rd</time></lecture></lecturelist><html><body><table border="1"><tr><td>Lecture name</td><td>Lecturer</td><td>Time</td>
</tr>
<tr>
<td> Knowledge Sharing Systems </td><td> Hideaki Takeda</td><td>
Wednesday/3rd</td></tr></table></body></html>Hideaki Takeda / National Institute ofWhey is XML not sufficient?
<person><name> Hideaki Takeda</name><age> 20</age></person><個人><名前>Hideaki Takeda</名前><年齢> 20</年齢></個人>

What are specified by “person” and “name” ?
l Is “name” and “名前” the same?
l Is this description sufficient as a description for “person”?
l …
ll

In short, syntax alone cannot solve these problems
Hideaki Takeda / National Institute ofArchitecture for the Semantic Web

Tim Berners-Lee http://www.w3.org/2002/Talks/09-lcs-sweb-tbl/

Hideaki Takeda / National Institute ofHow to describe “meaning”?
Need to describe “information on information”
n “Meaning of something” is a description (“meaning”) to a
description (“something”) in computersn Metadatau Data about datal Need to architecture for common understandingn Syntax (language or scheme)n Vocabulary (ontology)lHideaki Takeda / National Institute of

A Layer model for Semantic Weblll

RDF (Resource Description Framework)
n The most primitive model for metadata description
u SVO modelu Entity-Relation Modelu Semantic net
RDF Scheman Addition of “concept” to RDF
u class-subclass，constraints
OWLn More general concept description language
u Logical consistencyu Various class expressionsu Various constraints

Tim Berners-Lee http://www.w3.org/2002/Talks/09-lcs-sweb-tbl/
Hideaki Takeda / National Institute ofTwo origin of Semantic WeblFrom the viewpoint of Web Community
n More meaning, more knowledge
n HTML -> XML -> RDF -> RDF Schema -> OWL->XML schema ->l

From the viewpoint of Knowledge Sharing Community (AI)n From closed knowledge presentation to open KRu Not for depth but for widthu Not for completeness, but for possibilityn KIF, Ontolinga -> OKBC -> OWL

Hideaki Takeda / National Institute of