Response time of BPEL4WS constructors

Response time is an important factor for every software system and it becomes more salient when it is associated with introducing novel technologies, such as Web services. Most performance evaluation of Web services are focused toward composite Web services and their response time. One important limitation of existing work is in the fact that only constant or service exponential time distribution are considered. However, experimental results have shown that the Web services response times is typically heavy-tailed, in particulary, if there are heterogeneous. So, heavy-tailed response times should be considered in the dimensioning Web services. In this study, we propose analytical formulas for mean response times for structured BPEL constructors such as sequence, flow and switch constructors, etc. The difference with previous studies in the literature, is that we consider heterogenous servers, the number of invoked elementary Web services can be variable and the elementary Web services response times are heavy-tailed.