QoS Aspects in Web Services Compositions

In our previous work, we have proposed a formal QoS aware framework for Web services compositions based on quantitative Reo and quantitative constraint automata (QCA). In this work, we extend the previous one in two directions. First, we propose the logic QBTSL which is used for specifying and reasoning about non-functional properties of compositions. Second, we describe our approach for estimating QoS of compositions based on QoS of participant web services within the proposed framework. A case study is used to reflect the proposed concepts and a simple tool is developed to make the QoS estimation process, automatic.