语义网与本体技术导论AnIntroductiontotheSemanticWeb

1、语义网与本体技术导论 An Introduction to the Semantic Web and Ontology Technology 黄智生Zhisheng HuangVrije University AmsterdamThe Netherlandshuangcs.vu.nlChina 2005 1/从Google谈起starting from GoogleChina 2005 2/存在的问题Existing Problems China 2005 3/我们能不能做得更好？Can we do it better?基于语义的搜索Semantics-based search概念组合描述 c

2、oncept combination specification指定特定领域 domain specific逼近搜索 approximate search搜索代理 search agentChina 2005 4/语义网(Semantic Web)核心思想:给网络信息赋于确切定义的意义, 即语义。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

3、 co-operation.“Berners-Lee et al., 2001China 2005 5/语义是什么?What is the Semantics?Frege(1848-1925): Reference and SenseSyntax, Semantics, PragmaticsDenotational Semantics vs. Operational SemanticsMain features指称性 (denotation)唯一性(uniqueness)相关性(relatedness)China 2005 6/语义网想做什么？(What the Semantic Web wa

4、nts to do)机器可自动处理机器可理解Content is machine-understandable if it is bound to some formal description of itself (i.e. metadata).China 2005 7/HTML标识(HTML Markup)Zhisheng HuangAffiliation: Department of Computer ScienceFaculty of SciencesVrije University AmsterdamEmail: huang cs.vu.nlPhone: 31-20-4447740(

5、office)China 2005 8/XML标注XML-AnnotationsZhisheng HuangDepartment of Computer ScienceFaculty of SciencesVrije University Amsterdamhuang cs.vu.nl (31)-20-4447740China 2005 9/Data Structures结构化数据Structured Data:Database半结构化数据Semi-structured Data:HTML, XML, BibTex非结构化数据Non-structured Data:TextChina 2005

6、 10/关系数据库的XML表示XML representation of a relational databaseJohn1234567Mary7654321.member idnamephone001John1234567002Mary7654321AI groupChina 2005 11/文件类型定义Document Type Definition(DTD)!DOCTYPE researcher China 2005 12/ResearcherAffiliationhasDepartmentFacultyUniversityNamePhoneeMail1n数据模型Data ModelC

7、hina 2005 13/XML模式XML SchemaThe purpose of an XML Schema is to define the legal building blocks of an XML document, just like a DTD. China 2005 14/Why XML SchemasXML Schemas are extensible to future additions XML Schemas are richer and more useful than DTDs XML Schemas are written in XML XML Schemas

8、 support data types XML Schemas support namespaces China 2005 15/名字冲突Name ConflictsSince element names in XML are not fixed, very often a name conflict will occur when two different documents use the same names describing two different types of elements. If these two XML documents were added togethe

9、r, there would be an element name conflict because both documents contain a same element with different content and definition. China 2005 16/XML名字空间XML NameSpaceUsing Namespaces to solve Name ConflictsExamples:xmlns:namespace prefix=namespace xmlns:xsd=/2001/XMLSchema China 2005 17/可扩展标识语言模式XML Sch

10、ema China 2005 18/资源描述框架Resource Description Framework(RDF)Metadata is machine understandable information about web resources or anything that has an URI, it is represented as a set of independent assertions:http:/wasp.cs.vu.nl/sekt/dig/dig.pdfZhishengCreatorCeesCreatorTriple: T(subject, attribute,

11、values) China 2005 19/RDF: Dublin CoreThe Dublin Core provides properties for describing network objects, suitable for use by network search engines.The Dublin Core is a set of predefined properties for describing documents.The first Dublin Core properties were defined at the Metadata Workshop in Du

12、blin, Ohio in 1995 and is currently maintained by the Dublin Core Metadata Initiative.China 2005 20/Dublin Core Metadata InitiativeThe Dublin Core Metadata Initiative is an open forum engaged in the development of interoperable online metadata standards that support a broad range of purposes and bus

13、iness models. /China 2005 21/Annotating Metadata Guidance on expressing the Dublin Core within the Resource Description Framework (RDF) Eric Miller Paul Miller Dan Brickley Dublin Core; RDF; XML Dublin Core Metadata Initiative Dublin Core Data Model Working Group 1999-07-01 text/

14、html en China 2005 22/资源描述框架模式RDF Schema (RDFS)RDFS defines vocabulary for RDFOrganizes this vocabulary in a typed hierarchyClass, subClassOf, typeProperty, subPropertyOfdomain, rangeChina 2005 23/RDFSProf. MaWangPersonStudentProfessorsubClassOfsubClassOftypehasSuperVisordomainrangetypeChina 2005 24

15、/概念与本体Concepts and OntologiesPhilosophical discipline, branch of philosophy that deals with the nature and the organisation of reality.Science of Being (Aristotle, Metaphysics, IV,1)What is being?What are the features common to all beings?China 2005 25/Vocabulary and Ontology Controlled vocabulary (

16、Jernst 2003) : a list of controlled termsunambiguousnon-redundant definitionOntology: a controlled vocabulary expressed in an ontology representation language (Jernst 2003)China 2005 26/In computer science An ontology is an explicit specification of a conceptualization. Gruber93An ontology is a shar

17、ed understanding of some domain of interest. Uschold, Gruninger96There are many definitionsa formal specification EXECUTABLEof a conceptualization of a domain COMMUNITYof some part of world that is of interest APPLICATIONDefinesA common vocabulary of termsSome specification of the meaning of the ter

18、msA shared understanding for people and machinesChina 2005 27/Why develop an ontology?To make domain assumptions explicitEasier to change domain assumptionsEasier to understand and update legacy dataTo separate domain knowledge from operational knowledgeRe-use domain and operational knowledge separa

19、telyA community reference for applicationsTo share a consistent understanding of what information means.China 2005 28/本体的主要特征Key features of an Ontology概念层次性Concept hierarchy, 概念包含关系concept subsumption特殊与一般关系 InstanceOf Relation (Instances)部分与整体关系 PartOf Relation (property)China 2005 29/Why not othe

20、r alternatives一阶谓词逻辑 the first-order predicate logic集合论 set theory程序语言 programming languagesChina 2005 30/RDF(S) ReconsiderationNext step up from plain XML:(small) ontological commitment to modeling primitivespossible to define vocabularyHowever:no precisely described meaningunclear semantics, no cl

21、ean separation between:InstancesConceptsMeta-ontologies (e.g. RDFS language itself)no inference modelChina 2005 31/China 2005 32/网络本体语言Web Ontology Language (OWL)OWL is built on top of RDF OWL is for processing information on the web OWL was designed to be interpreted by computers OWL was not design

22、ed for being read by people OWL is written in XML OWL is a web standard China 2005 33/Design Goals for OWLChina 2005 34/Layered language OWL Lite:Classification hierarchySimple constraints OWL DL:Maximal expressivenessWhile maintaining tractabilityStandard formalisation OWL Full:Very high expressive

23、nessLoosing tractabilityNon-standard formalisationAll syntactic freedom of RDF(self-modifying)Syntactic layeringSemantic layeringFullDLLiteChina 2005 35/China 2005 36/China 2005 37/China 2005 38/OWL Example: animals China 2005 39/China 2005 40/Semantic Web LayersChina 2005 41/语义网的逻辑基础Logical Foundat

24、ion of the Semantic Web描述逻辑与框架逻辑之争Description Logic vs. Frame-Logic封闭世界假说与开放世界假说Closed world assumption vs. Open world assumption唯一名假说与非唯一名假说Unique name assumption vs. Non-unique name assumption面向对象与非面向对象Object-oriented vs. non-object oriented.China 2005 42/描述逻辑 Description LogicKnowledge BaseTbox (

25、schema)Abox (data)Man Human u MaleHappy-Father Man u 9 has-child Female u John : Happy-FatherhJohn, Maryi : has-childInference SystemInterfaceChina 2005 43/Basic Description Logic: ALConcept Expressions:A (atomic concept) (universal concept) (bottom concept) A (atomic negation)C D (intersection)R.C

26、(value restriction)R.T (limited existential quantification)where A is a concept name, C and D are concept expressions, and R is a role expressionChina 2005 44/Family of AL languageC D (Union)R.C (Full Existential Quantification) C (Complement)Number restriction( n R) (at least restriction)( n R) (at

27、 most restriction)Qualified number restriction( n R.C) (at least restriction)( n R.C) (at most restriction)Transitive Role: R+Inverse of Role: IRole Hierarchies R S: HChina 2005 45/Exampleswoman person femaleman person womanmother woman hasChild.personfather man hasChild.personChina 2005 46/Decidabl

28、e Subset of First-Order Logic Equivalent to 3 Variable Fragment (Borgida 1996)Model theoretic semantics by mapping to abstract domainProvides Primitives for defining Conceptual KnowledgeConcept Expressions (Formulas with 1 free variable) for describing Sets of ObjectsBoolean Operators: C D, C D, CQu

29、antifiers: (R.C), (P.C) Cardinality Constraints: (= n R), ( n R), (abraham; mother-sarah.ishmael:manfather-abraham; mother-hagar:woman.jacob:manfather-isaac; mother-rebekah:woman.esau:manfather-isaac; mother-rebekah./* rules consisting of a rule head and a rule body */FORALL X,Y Xson-Y X.FORALL X,Y

30、Xson-Y X.FORALL X,Y Xdaughter-Y X.FORALL X,Y Xdaughter-Y X./* query */FORALL X,Y Yfather-abraham.China 2005 51/Semantic Web Application: the foaf projectThe Friend of a Friend (FOAF) project is about creating a Web of machine-readable homepages describing people, the links between them and the thing

31、s they create and do. http:/www.foaf-/China 2005 52/China 2005 53/Foaf.rdf Huang Zhisheng Huang Zhisheng male 238a59a17bd96fbb93f39aa9dba2f6847a8d261c mailto:huangcs.vu.nl Annette ten Teije c10984c365331f1d38f649adccbb7aac5873aed2 China 2005 54/China 2005 55/Add the FOAF information on the homepage

32、. . FOAF Agents on the Internet will now be able to locate the FOAF entry. China 2005 56/FOAFBot: IRC Community Support AgentFOAFBot is an IRC bot that provides access to a knowledge base created by spidering FOAF files.It can sit on an IRC channel and provide basic informational help about the memb

33、ers of a community.China 2005 57/DOPEThe DOPE Browser is a deliverable created by Aduna BV for the Drug Ontology Project for Elsevier (DOPE), a project funded by the Elsevier Advanced Technology Group. China 2005 58/China 2005 59/China 2005 60/China 2005 61/Variants of ontologies具体领域的本体 Domain ontol

34、ogy: domain specific ontology.Upper Ontology: limited to concepts that are meta, generic, abstract and philosophical, general enough to address (at a high level) a broad range of domain areas. China 2005 62/Suggested Upper Merged Ontology (SUMO)/SUMO is written in the SUO-KIF language Largest free,

35、formal ontology available, with 20,000 terms and 60,000 axioms when all domain ontologies are combined. China 2005 63/SUMOThese consist of SUMO itself, the MId-Level Ontology (MILO), and ontologies ofCommunicationsCountries and RegionsDistributed computing, EconomyFinance,Engineering componentsGeogr

36、aphy, Government, Military, PeopleTransportationChina 2005 64/基因本体Gene Ontology/Controlled vocabulary to describe gene and gene product attributes in any organism. Updated every 30 minutes 9759 biological_process1574 cellular_component7076 molecular_function (up to 16/8/200

37、5) Format: Obo, GO, OWLChina 2005 65/语义网核心研究课题：SEKT ProjectSemantically Enabled Knowledge Technologies (SEKT)A European research and development project launched under the EU Sixth Framework Programme.China 2005 66/Duration and PartnersThree year project: January 2004 December 2006.13 partners:公司： B

38、T(英国电信), Empolis GmbH, iSOCO(Spain), Kea-pro GmbH, Ontoprise, Sirma AI EOOD(Bulgaria), (+SIEMENS西门子公司)大学： Jozef Stefan Institute(Slovenia), Univ. Karlsruhe(Germany), Univ. Sheffield(U.K.), Univ. Innsbruck(O), Univ. Autonoma Barcelona(Spain), Vrije Universteit Amsterdam(The Netherlands)China 2005 67/

39、Case StudiesLegal Domain (iSOCO)Telecom Domain (BT)Siemens China 2005 68/SEKT Activities and RelationshipsChina 2005 69/Core Tasks: WP3China 2005 70/Main Goals of WP3Enable and greatly facilitate setting up, usage and maintenance of Ontologies and related MetadataCombine manual and (semi-) automatic approaches for evolution of Ontologies and related MetadataMake extensive use of reasoningAIFBChina 2005 71/Task OverviewIncremental Ontology