The Application of WSFL in the Parlay X Based Services Creation

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【出版日期】2005-03-25

【刊名】The Journal of China Universities of Posts and Telecommunications

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1 Introduction NGN abstracts beneath protocols as a set of easy under standing interfaces through open Application ProgrammingInterfaces (API). These APIs are independent with net works, so the services created with these APIs are irrespec tive to special network details[1] ParlayXAPI is a set of more single and higher abstractedAPIs than Parlay API. These ParlayXAPIs have the abilityto access the network functions, and are easy to understandby IT developers to use in the development of categories ofnew services. ParlayX opens these APIs through Web Ser vice technology. Usually, developers use C++ or Java in developing ser vice based on Parlay or ParlayX[2]. With the rising of eX tensible Markup Language ( XML) technology, more andmore markup languages based on XML are adopted to de scribe telecommunication services[7], such as the ServiceCreation Markup Language(SCML) of JAIN, and Call Pro cessing Language(CPL) of IETF. Owing to the fact that Par lay X opens interfaces through Web Services, we proposedescribing ParlayX based services using WSFL. In this paper, Parlay X Web Service infrastructure andservice modeling with WSFL are introduced, an instance toof Parlay X based service description with WSFL and theexecution of WSFL script is demonstrated, and then theproblems caused by WSFL application in this area are ana lyzed.2 Parlay X Web Service and WSFL At the beginning, we briefly illustrate ParlayXWeb Ser vice infrastructure and service modeling with WSFL.2 1 Parlay X Web Service Infrastructure Parlay X API[3] is composed of simple and abstracttelecommunication function modules. It screens the details ofall the communication process, which makes developers in cluding IT service developers can quickly understand and usethem to create new services. Web Service is a kind of soft ware component technology. It describes services with WebService Description Language(WSDL), publishes and dis covers service through Universal Description, Discovery, andIntegration(UDDI), and invokes remote operations throughHypertext Transfer Protocol(HTTP) or Simple Object AccessProtocol(SOAP). Parlay XWeb Service provides Parlay XAPI invoking through Web Service. Parlay organization pro vides interfaces description with WSDL. ParlayXWeb Service covers the capability sets of ParlayAPIs and the Web Service technology. Its infrastructure isdepicted in Fig.1. In the infrastructure, three roles are presented: (1) Parlay X Web Service Gateway: It is a server thatcan provide one or more Parlay X Web Services, in whichall the fundamental telecommunication services are included; (2) Application Server: It executes service logic, and in vokes the fundamental service in the Parlay X Web ServiceGateway; (3) Parlay Service Proxy: It takes charge of such worksas registration, management and search of services, and it is a promulgator of services.Fig.1 ParlayXWeb Service infrastructure[4]2 2 Service Modeling with WSFL WSFL is drafted by IBM for work flow in the following twolayers: it takes a directed graph model approach to definingand executing business processes; it defines a public inter face that allows business processes to advertise themselves asWeb Services[5~6]. WSFL uses the following two models todescribe these two layers: flow model and global model. The flow model describes how to organize existing WebServices to implement a new work flow, and it schedules theexecution order of these Web Services; The global model de scribes how to export the composed new work flow as a WebService, which depicts the interaction of composed serviceand existing services. The flow model depicts a work flow. It has three mainroles: activity (action need to execute), control link (exe cution path of activities), and data link (information transferbetween two activities). In the WSFL script, there are re spective main nodes: activity, controlLink and dataLink.There are also other main modes: serviceProvider and mes sage, which respectively describe service providers who im plement the activities and interaction messages used in ser vice invoking. Here, we innovatively try to introduce this work flow de scription language to describe services based on Parlay XWeb Service.3 Application of WSFL in Service Cre ation Based on Parlay Xaims at composing the existing Parlay X Web Services as awork flow to create new service which satisfies our new re quirements. So the flow model of WSFL is helpful. On the other side, the global model of WSFL can exportthe composed work flow as a new web service, which can beused as the implementation of an activity in the new servicework flow. Through the reduplicate use of these tow models,we can achieve recursive service creation. So global model ofWSFL can satisfy the requirement of service integration ofParlayXWeb Service. Based on the above two facts, we try to apply WSFL toservice creation based on ParlayXWeb Service.3 1 An Instance of WSFL Description of Service Ba

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