10-服務(wù)計(jì)算基礎(chǔ)(語義Web服務(wù))

1、服務(wù)計(jì)算基礎(chǔ)1第九章 語義Web服務(wù)2主要內(nèi)容概述語義網(wǎng)語義Web服務(wù)3第一節(jié) 概述4語義是事物的觀察者給事物本身賦予的含義，一致共享的語義構(gòu)成觀察者對(duì)事物的知識(shí)，是觀察者之間互相交流的基礎(chǔ)。語義網(wǎng)通過給萬維網(wǎng)上的文檔(如:HTML)添加能夠被計(jì)算機(jī)理解的語義(Meta data)，從而使整個(gè)萬維網(wǎng)中現(xiàn)存的信息發(fā)展成一個(gè)巨大的全球信息庫、知識(shí)庫。語義和語義網(wǎng)5Web 服務(wù)使用標(biāo)準(zhǔn)的、規(guī)范的 XML進(jìn)行描述，包括消息格式、傳輸協(xié)議和位置，隱藏了實(shí)現(xiàn)服務(wù)的細(xì)節(jié)。WSDL從句法層面對(duì)Web服務(wù)的功能進(jìn)行描述，包括4個(gè)不同的方面：數(shù)據(jù)類型、消息、操作和訪問端口。這只是提供了Web服務(wù)的接口描述，對(duì)服務(wù)

2、的行為約束和屬性描述缺乏進(jìn)一步的支持。缺陷數(shù)據(jù)管理有序性與Web上信息無序性；搜索引擎查全查準(zhǔn)要求與服務(wù)描述缺語義；信息獲取效率與Web海量動(dòng)態(tài)數(shù)據(jù)。語義Web服務(wù)6語義Web服務(wù)的主要方法是利用Ontology來描述Web服務(wù)，通過帶有語義信息的Web服務(wù)來實(shí)現(xiàn)服務(wù)的自動(dòng)發(fā)現(xiàn)，調(diào)用和組合。語義Web和Web 服務(wù)是語義Web服務(wù)的兩大支撐技術(shù)。OWL-S是連接兩大技術(shù)的橋梁。目前對(duì)語義Web服務(wù)標(biāo)記語言研究最典型的組織就是DARPA（Defence Advanced Research Projects Agency）組織，其研究組OWL Services Coalition提出了語義Web服

3、務(wù)標(biāo)記語言O(shè)WL-S語義Web服務(wù)7第二節(jié) 語義網(wǎng)8Semantic Web的由來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的定義10Semantic Web的架構(gòu)的相關(guān)標(biāo)準(zhǔn) 本體層1.以謂詞演算為基礎(chǔ)的語言KIF-based Ontolingua,CycL,Loom,Frame-Logic2.基于XM

7、L的本體表示語言SHOE,XOL,OML&CKML,RDFS,Riboweb,OIL,DAML+OIL,OWL規(guī)則層RuleML、HornML、DLML邏輯框架層FOL、HOL、DL、Horn-logic、OMDoc下四層已經(jīng)發(fā)展的比較成熟與完善1.數(shù)據(jù)格式層2.信息表示層3.元數(shù)據(jù)表示層4.元數(shù)據(jù)定義層5.本體層6.規(guī)則層7.邏輯框架層8.證據(jù)層9.高信度Web層We are here!11本體(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? 本體(ontology)的定義12 Ontology is a formal, explicit specification of a shared conceptualization Gruber 要點(diǎn)：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 本體(ontology)的

10、定義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 本體(ontology)的定義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本體的構(gòu)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本體的構(gòu)成16Instancesrepresent specific elementssuch as: Student called Peter is an instance of Student class本體的構(gòu)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)資源描述框架(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資源描述框架模式(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資源描述框架模式(RDFS)21Some important terminologies in RDFSrdf:type 類的實(shí)例和類之間的關(guān)系rdfs:subClassOf 子類和類之間的關(guān)系rdfs:subPropertyOf 子性質(zhì)關(guān)系rdfs:domain 性質(zhì)的定義域rdfs:range 性質(zhì)的值域資源描述框架模式(RDFS)22RDF和RDFS的關(guān)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本體描述語言O(shè)WL25OWL 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第三節(jié) 語義Web服務(wù)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語義Web服務(wù)標(biāo)記語言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整體結(jié)構(gòu)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服務(wù)概要ResourceServiceServiceProfileServiceModelServiceGroundingprovidespresents(what it does)describedby(how it works) supports(how to access)43服務(wù)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服務(wù)概要45Summarizes the abstract capability of a serviceFunctional specification ofwhat the s

32、ervice providesin terms of parameters,subclassed as:preconditionsinputsoutputseffects服務(wù)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服務(wù)概要功能性描述：參數(shù)47Provides supporting information about the serviceThese

34、includeserviceNametextDescriptionhas_processqualityRatingserviceParameterserviceCategorycontactInformation服務(wù)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服務(wù)概要層次49服務(wù)概要層次：例子50ResourceServiceServiceProfileServiceModelServiceGroundingprovidespresents(what it does)describedby(how it works) supports(how to access)服務(wù)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服務(wù)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)服務(wù)模型：過程本體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)服務(wù)模型：OWL-S中的過程類型54服務(wù)模型：總體結(jié)構(gòu)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