10-服务计算基础(语义Web服务)

1、服务计算基础1第九章 语义Web服务2主要内容概述语义网语义Web服务3第一节 概述4语义是事物的观察者给事物本身赋予的含义，一致共享的语义构成观察者对事物的知识，是观察者之间互相交流的基础。语义网通过给万维网上的文档(如:HTML)添加能够被计算机理解的语义(Meta data)，从而使整个万维网中现存的信息发展成一个巨大的全球信息库、知识库。语义和语义网5Web 服务使用标准的、规范的 XML进行描述，包括消息格式、传输协议和位置，隐藏了实现服务的细节。WSDL从句法层面对Web服务的功能进行描述，包括4个不同的方面：数据类型、消息、操作和访问端口。这只是提供了Web服务的接口描述，对服务

2、的行为约束和属性描述缺乏进一步的支持。缺陷数据管理有序性与Web上信息无序性；搜索引擎查全查准要求与服务描述缺语义；信息获取效率与Web海量动态数据。语义Web服务6语义Web服务的主要方法是利用Ontology来描述Web服务，通过带有语义信息的Web服务来实现服务的自动发现，调用和组合。语义Web和Web 服务是语义Web服务的两大支撑技术。OWL-S是连接两大技术的桥梁。目前对语义Web服务标记语言研究最典型的组织就是DARPA（Defence Advanced Research Projects Agency）组织，其研究组OWL Services Coalition提出了语义Web服

3、务标记语言OWL-S语义Web服务7第二节 语义网8Semantic Web的由来Web was “invented” by Tim Berners-Lee , a physicist working at CERNTBLs original vision of the Web was much more ambitious than the reality of the existing (syntactic) Web:TBL (and others) have since been working towards realising this vision, which has becom

4、e known as the Semantic WebE.g., article in May 2001 issue of Scientific American“. a goal of the Web was that, if the interaction between person and hypertext could be so intuitive that the machine-readable information space gave an accurate representation of the state of peoples thoughts, interact

5、ions, and work patterns, then machine analysis could become a very powerful management tool, seeing patterns in our work and facilitating our working together through the typical problems which beset the management of large organizations.”9The Semantic Web is an extension of the current web in which

6、 information is given well-defined meaning, better enabling computers and people to work in co-operation. Tim Berners-Lee, James Hendler, Ora Lassila, The Semantic Web, Scientific American, May 2001Semantic Web的定义10Semantic Web的架构的相关标准 本体层1.以谓词演算为基础的语言KIF-based Ontolingua,CycL,Loom,Frame-Logic2.基于XM

7、L的本体表示语言SHOE,XOL,OML&CKML,RDFS,Riboweb,OIL,DAML+OIL,OWL规则层RuleML、HornML、DLML逻辑框架层FOL、HOL、DL、Horn-logic、OMDoc下四层已经发展的比较成熟与完善1.数据格式层2.信息表示层3.元数据表示层4.元数据定义层5.本体层6.规则层7.逻辑框架层8.证据层9.高信度Web层We are here!11本体(ontology)a philosophical discipline, branch of philosophy that deal with the nature and the organiz

8、ation of reality.Science of beingTries to answer the questions:what is being?what are the features common to all beings? 本体(ontology)的定义12 Ontology is a formal, explicit specification of a shared conceptualization Gruber 要点：Conceptualization: an abstract model of phenomena in the world by having ide

9、ntified the relevant concepts of those phenomena.Explicit: the type of concepts used, and the constraints on their use are explicitly defined. Formal: the fact that the ontology should be machine readable. Shared: ontology should capture consensual knowledge accepted by the communities 本体(ontology)的

10、定义13What is a concept?Different communities have different notions on what a concept means:formal conceptsconcept label terminologyframe or OOThere is m:n relationship between words and conceptsdifferent words may refer to the same conceptsa word may refer to several conceptsOntology languages shoul

11、d provide means for making this difference explicit 本体(ontology)的定义14Classesconcepts of the domain or tasks, which are usually organized in taxonomiesin univ-ontology: student and professor are two classesRelationsa type of interaction between concepts of the domainsuch as: subclass-of, is-a本体的构成15F

12、unctionsA special case of relations in which the n-th element of the relationship is unique for the n-1 preceding elementsSuch as: Price-of-a-used-car can define the calculation of the price of the second-hand car on the car-model, manufacturing data and kilometersAxioms（公理）Model sentences that are

13、always trueSuch as: if the student attends both A and B course, then he or she must be a second year student本体的构成16Instancesrepresent specific elementssuch as: Student called Peter is an instance of Student class本体的构成17RDF data modelResourcesA resource is a thing you talk about (can reference)Resour

14、ces have URIs (Uniform Resource Identifiers)RDF definitions are themselves ResourcesPropertiesA special kind of resources, describe relations between resources. (subject, predicate, object)资源描述框架(RDF)18 Discrete Mathematics David Billington Associate Professor RDF19Classes and propertiesclasses: a s

15、et of objects, rdfs:Classinstances: individual objectproperty: add restrictions on objects, rdfs: PropertyClass and hierarchies资源描述框架模式(RDFS)20Restrictions: Courses must taught by academic staff members onlyMichael Maher is a professorif we know, professor is a sub class of academic staff Michael Ma

16、her is allowed to teach coursesProperty hierarchies资源描述框架模式(RDFS)21Some important terminologies in RDFSrdf:type 类的实例和类之间的关系rdfs:subClassOf 子类和类之间的关系rdfs:subPropertyOf 子性质关系rdfs:domain 性质的定义域rdfs:range 性质的值域资源描述框架模式(RDFS)22RDF和RDFS的关系23RDF/RDFS limitationsLocal scope of properties. cows eat only plan

17、tsDisjointness of classes. Male and femaleBoolean combinations of classes. (, )Cardinality restrictions, property value restriction. person and parents, teacher and coursesSpecial characteristics of propertiesSupervise and IsSupervisedbyRDF的局限性24Requirements for ontology languagea well-defined synta

18、xa formal semantics (convenient to reason)convenience of expressionefficient reasoning supportsufficient expressive power本体描述语言OWL25OWL 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 designed for being read by people OW

19、L is written in XML OWL is a web standard 什么是OWL26Origins of OWLDAMLDAML+OILDAML = DARPA Agent Markup LanguageOIL = Ontology Inference LayerOWL is now a W3C Recommendation!OILOWLRDFAll were influenced by RDFOWL27Logic foundation of OWL: Description LanguageOWL Lite:Classification hierarchySimple con

20、straints OWL DL(Description Logic):Maximal expressivenessWhile maintaining tractabilityStandard formalisation OWL Full:Very high expressivenessLoosing tractabilityNon-standard formalisationAll syntactic freedom of RDF(self-modifying)Syntactic layeringSemantic layeringFullDLLiteLayered language of OW

21、L28OWL29OWL30OWL31 OWL Example: animals32第三节 语义Web服务33WWWURI, HTML, HTTPBringing the web to its full potentialSemantic WebRDF, RDF(S), OWLDynamicWeb ServicesUDDI, WSDL, SOAPStaticSemantic WebServicesMotivation of Semantic Web Service34 Semantic Web Technology + Web Service TechnologySemantic Web Ser

22、vices=Semantic Web Services allow machine supported data interpretation ontologies as data model automated discovery, selection, composition, and web-based execution of servicesas integrated solution for realizing the vision ofthe next generation of the Web.35Semantic Web ServicesDefine exhaustive d

23、escription frameworks for describing Web Services and related aspects (Web Service Description Ontologies) Support ontologies as underlying data model to allow machine supported data interpretation (Semantic Web aspect) Define semantically driven technologies for automation of the Web Service usage

24、process (Web Service aspect) 36Semantic Web ServicesUsage Process:Publication: Make the available description of the capability of a service Discovery: Locate different services suitable for a given task Selection: Choose the most appropriate services among the available ones Composition: Combine se

25、rvices to achieve a goalMediation: Solve mismatches (data, protocol, process) among the combined Execution: Invoke services following programmatic conventions 37Semantic Web ServicesExecution support: Monitoring: Control the execution processCompensation: Provide transactional support and undo or mi

26、tigate unwanted effectsReplacement: Facilitate the substitution of services by equivalent onesAuditing: Verify that service execution occurred in the expected way 38Semantic Web ServicesWith Semantic: Not only an interface description, but also the capability of the service.Logic reasoning enhanced

27、service discovery and composition.Can be done automatically.39OWL-S: Ontology Web Language for ServicesWSMLWSDL-S语义Web服务标记语言40OntologyOWL-S is an OWL ontology to describe Web servicesOWL-S leverages on OWL toSupport capability based discovery of Web servicesSupport automatic composition of Web Servi

28、cesSupport automatic invocation of Web servicesComplete do not competeOWL-S does not aim to replace the Web services standardsrather OWL-S attempts to provide a semantic layer OWL-S relies on WSDL for Web service invocation (see Grounding)OWL-s Expands UDDI for Web service discovery (OWL-S/UDDI mapp

29、ing)OWL-S概述41OWL-S整体结构ResourceServiceServiceProfileServiceModelServiceGroundingcommunication protocol (RPC, HTTP, )port numbermarshalling/serializationinput typesoutput typespreconditionseffectsprocess flowcomposition hierarchyprocess definitionsprovidespresents(what it does)describedby(how it works

30、) supports(how to access)42服务概要ResourceServiceServiceProfileServiceModelServiceGroundingprovidespresents(what it does)describedby(how it works) supports(how to access)43服务概要Service ProfilePresented by a service.Representswhat the service providesTwo main uses:Advertisements of Web Services capabilit

31、ies (non-functional properties, QoS, Description, classification, etc.)Request of Web services with a given set of capabilitiesPro not specify use/invocation!44Non Functional PropertiesFunctionality Description服务概要45Summarizes the abstract capability of a serviceFunctional specification ofwhat the s

32、ervice providesin terms of parameters,subclassed as:preconditionsinputsoutputseffects服务概要功能性描述46PreconditionsSet of conditions that should hold prior to service invocationInputsSet of necessary inputs that the requester should provide to invoke the serviceOutputsResults that the requester should exp

33、ect after interaction with the service provider is completedEffectsSet of statements that should hold true if the service is invoked successfullyOften refer to real-world effectsPackage being delivered, or Credit card being debited服务概要功能性描述：参数47Provides supporting information about the serviceThese

34、includeserviceNametextDescriptionhas_processqualityRatingserviceParameterserviceCategorycontactInformation服务概要非功能性描述48Sub-classing the Pro facilitates the creation and specialisation of service categoriesEach subclass can:Introduce new propertiesPlace restrictions on existing propertiesSub-classing

35、can also be used to specialise requests for serviceAn example Pro is provided, but others could just as easily be defined服务概要层次49服务概要层次：例子50ResourceServiceServiceProfileServiceModelServiceGroundingprovidespresents(what it does)describedby(how it works) supports(how to access)服务模型51Service ProcessDes

36、cribes how a service works: internal processes of the serviceSpecifies service interaction protocolSpecifies abstract messages: ontological type of information transmittedFacilitates(automated) Web service invocationcompositioninteroperationmonitoring服务模型：描述方法52The basic class of the Process Ontolog

37、y is the Process. Its subclasses describe each process by:any number of (possibly, conditional) inputs;any number of (possibly, conditional) outputs;any number of preconditions, which must hold in order for the process to be invoked;any number of (possibly, conditional) side effects;any number of pa

38、rticipants (subprocess)服务模型：过程本体53Atomic processes: directly invokable (by an agent), have no subprocesses, executed in a single stepComposite processes: consist of other (non-composite or composite) processesThey have a composedOf property, by which the control structure of the process is indicated

39、, using a ControlConstruct subclasses (see table )Simple processes: abstract concepts, used to provide a view of some atomic process, or a simplified representation of some composite process (i.e., the “black box” view of a collapsed composite process)服务模型：OWL-S中的过程类型54服务模型：总体结构55ConstructDescriptio

40、nSequenceExecute a list of processes in a sequential orderConcurrentExecute elements of a bag of processes concurrentlySplitInvoke elements of a bag of processesSplit+JoinInvoke elements of a bag of processes and synchronizeUnorderedExecute all processes in a bag in any orderChoiceChoose between alternatives and execute oneIf-then-elseIf specified condition hold, execute “Then”, else execute “Else”.Repeat-UntilIterate execution of a bag of processes until a condition holdsRepeat-WhileIterate execution of a b