Modeling Cost-Aware Web Services Composition Using PTCCS

Process algebra are a set of formal languages that are suitable to describe concurrent and communication systems including Web services. Nowadays, although process algebra have been effectively exploited for modeling and verifying functional aspects of Web services composition, non-functional aspects have been ignored due to process algebra lack of capability of modeling them. Since execution of Web services need to consume resource (and energy, time, fee, etc), we propose an abstract concept, that is, cost, to model this non-functional aspect. We introduce this abstract concept into TCCS(temporal calculus of communicating systems) that is a classical process algebra and propose a new process algebra called PTCCS(priced temporal calculus of communicating systems). We present syntax and semantics of PTCCS, and prove that PTCCS extends TCCS with cost modeling capability. And an algorithm is proposed to construct cost state space that is used to select Web services composition with optimal cost. Experiment results show that PTCCS can model both functional aspects and non-functional aspects of Web services composition.