A Web Service Model Based on Partial Order Event Structure and its Formal Composition
Ting Han · 2005
with the development of Internet, a software service computing environment based on Web has come into being. At the same time, as the requirement of large-scale applications, it is often not sufficient for single Web ser- vice to support some complicated applications. As a result, the composition of Web services becomes even more im- portant. Due to the interaction and coordination between Web services, distribution and concurrency are two essential characteristics of the software service distributed system, which makes it difficult to ensure the correctness of the composition. Thus a mechanism supporting composition should be provided. Moreover, the efficiency of the software service distributed system is also worth considering. This paper investigates these problems from the point of formal- ism. Partial order relation, as an ideal and effective means, is utilized because of the natural partial order relation a- mong Web services. Based on this, this paper gives a formal model of Web services based on partial order event mul- tisets from the perspective of composition. We deal with the concurrency problem from finer grain of event inside the Web service itself other than the whole Web service, which makes it possible for more events in one Web service or from different Web services to execute concurrently and thus improve the efficiency. Furthermore, a Web service composition language is given with the rules that ensure an efficient composition when correctness is guaranteed. Some examples are invited to demonstrate the advantages of our model and composition approach.