An evolution model of composed service based on global dependence net

Web service composition is a major way of constructing SOA-based applications. However, as uses' requirements change, web services have to be recomposed correspondingly once again from the scratch. It will be rather time-consuming, error-prone and mostly fussy. To tackle the widespread requirements changes, we propose a novel approach that can make an existing composed service automatically grade to reach another new composed service in an evolutionary manner according to user's requirements. An evolution model called control structure net is built to formally represent composition structure of a certain composed service based on interface dependence. Furthermore, a global dependence net, which provides an evolution knowledge base, is constructed by modeling all available web services. Evolution process is presented in detail and evolution reasoning algorithms are given to automatically remove invalid paths and make up necessary paths. Experimental results show that our proposed approach can correctly evolve to target composed service, and its performance also greatly surpasses that of classic service composition approach.