Unified Modelling functional and Non-functional Aspects of Web Services Composition Using PTCCS

Unified modelling and analyzing functional and non-functional aspects of Web services composition reduces the gap caused by modelling them in different models respectively, increases development speed, and reduces development cost. Though existing process algebras have advantages over modelling concurrent and composite systems, including Web services composition, they lack the capability of modelling cost that is an important non-functional property. This paper proposes a process algebra called PTCCS (Priced Temporal Calculus of Communicating Systems) based on the existing TCCS (Temporal Calculus of Communicating Systems) by associating action of TCCS with price information. The authors present the syntax and semantics of PTCCS and prove that PTCCS extends TCCS with cost modelling capability. Cost state space for a process in PTCCS is proposed and an algorithm to generate it to support cost optimal Web services composition or time optimal Web services composition is presented. The authors present another algorithm that can generate cost optimal path for cost optimal Web services composition and time optimal path for time optimal Web services composition based on cost state space. An experiment shows that PTCCS can effectively support unified modelling functionality, time, and cost of Web services composition.