A Petri-Net-Based Approach to QoS Estimation of Web Service Choreographies

Current Web service choreography proposals, such as WSCI and BPEL, provide notations for describing the message flows in Web service collaborations. The kernel of WSCI consists of simple communication primitives that may be combined using control-flow constructs expressing sequence, branching, parallelism, synchronization, etc. Many efforts have been made on functional formalization and property verification of WSCI-based service choreography. However, QoS facet of service is yet to be given the importance it deserves. In this paper, we introduce a novel analytical approach to predict the QoS of web service choreographed based on WSCI using general stochastic Petri net (GSPN) as the intermediate representation. From the GSPN model and its corresponding continuous-time Markov chain, analytical estimation of three QoS metrics are obtained. In the case study, we also use computer simulation and confidence interval analysis to validate theoretical evaluations.