An Integrated Framework for Web Services Orchestration

Currently, Web services give place to active research and this is due both to industrial and theoretical factors. On one hand, Web services are essential as the design model of applications dedicated to the electronic business. On the other hand, this model aims to become one of the major formalisms for the design of distributed and cooperative applications in an open environment (the Internet). In this paper, we will focus on two features of Web services. The first one concerns the interaction problem: given the interaction protocol of a Web service described in BPEL, how to generate the appropriate client? Our approach is based on a formal semantics for BPEL via process algebra and yields an algorithm which decides whether such a client exists and synthetize the description of this client as a (timed) automaton. The second one concerns the design process of a service. We propose a method which proceeds by two successive refinements: first the service is described via UML, then refined in a BPEL model and finally enlarged with JAVA code using JCSWL, a new language that we introduce here. Our solutions are integrated in a service development framework that will be presented in a synthetic way.

International Journal of Business Process Integration and Management, 2006

We argue that essential facets of web services, and especially those useful to understand their interaction, are best described using process-algebraic notations. Web service description and execution languages such as BPEL are essentially process description languages; they are based on primitives for behaviour description and message exchange which can also be found in more abstract languages such as process algebras. One legitimate question is therefore whether the web services community can benefit from the sophisticated languages and tools developed in the process algebra area. Our investigations suggest a positive answer, and we claim that process algebras provide solutions to a number of challenges raised by the web services paradigm, among which are central issues of orchestration and choreography. We show on a case study that readily available tools based on process algebra are effective at verifying that compositions of services obtained by choreography and orchestration conform their requirements and respect properties. We suggest a general framework based on a mapping between process algebra and web services written in BPEL, and illustrate both the modelling of services by process algebra and the use of reasoning tools.

Packt Publishing Ltd

2007

We introduce COWS (Calculus for Orchestration of Web Services), a new foundational language for SOC whose design has been influenced by WS-BPEL, the de facto standard language for orchestration of web services. COWS combines in an original way a number of ingredients borrowed from wellknown process calculi, e.g. asynchronous communication, polyadic synchronization, pattern matching, protection, delimited receiving and killing activities, while resulting different from any of them. Several examples illustrates COWS peculiarities and show its expressiveness both for modelling imperative and orchestration constructs, e.g. web services, flow graphs, fault and compensation handlers, and for encoding other process and orchestration languages. We also present an extension of the basic language with timed constructs.

2006

icics.info

Abstr act. When set of basic web service is built, the next step is to create more complex one. A programmatic approach uses declarative language such as BPEL. This kind of representation is verbose and needs assistance for the creation of business process. We defined a generative strategy leading by formal specification. Because, web service composition languages use standard operators like sequence, choice and parallel; process algebras are right candidate for their design. We use higher order pi calculus for specification of orchestration and consider it as a basis for generating BPEL skeleton. After enrichment of BPEL definition, we interpret it by mobile agents. They play role of a conductor which evaluates a part or a whole BPEL definition. This mobile engine reduces message traffic by replacing message transfer into local message operating. We use mobile agent as distributed conductor of business processes.

2004

With the development of the semantic Web, the specification of Web services has evolved from a "remote procedure call" style to a behavioral description including standard constructors of programming languages. Such a transformation introduces new problems since traditional clients will not be able to interact with these sophisticated services. In this work, we develop a generic agent capable to fully control the interaction process with a Web service given its XLANG behavioral description (XLANG being one of these languages). At first, we give an operational semantic to XLANG in terms of timed transition systems. Then we define a relation between two communicating systems which formalizes the concept of a correct interaction and we propose an algorithm which either detects ambiguity of the Web service or generates a timed deterministic automaton which controls the agent behavior during the interaction with the service. Starting from these theoretical developments we have built a platform which ensures to a user the correct handling of any complex Web service dynamically discovered through the Web.

… of the 15th international conference on …, 2006

A Service oriented system emerges from composition of services. Dynamically composed reactive Web services form a special class of service oriented system, where the delays associated with communication, unreliability and unavailability of services, and competition for resources from multiple service requesters are dominant concerns. As complexity of services increase, an abstract design language for the specification of services and interaction between them is desired. In this paper, we present ASDL (Abstract Service ...

Bridging People and Software through Process Technology, 2005

Electronic Notes in Theoretical …, 2004

Current Web service choreography proposals, such as BPEL4WS, BPSS, WSFL, WSCDL or WSCI, provide notations for describing the message flows in Web service collaborations. However, such proposals remain at the descriptive level, without providing any kind of reasoning mechanisms or tool support for checking the compatibility of Web services based on the proposed notations. In this paper we present the formalization of one of these Web service choreography proposals (WSCI), and discuss the benefits that can be obtained by such formalization. In particular, we show how to check whether two or more Web services are compatible to interoperate or not, and, if not, whether the specification of adaptors that mediate between them can be automatically generated -hence enabling the communication of (a priori) incompatible Web services.