Automation of Web service composition is one of the most interesting challenges facing the Semantic Web today. In this paper we propose a mean of performing automated Web service composition by exploiting semantic matchmaking between Web service parameters (i.e., outputs and inputs) to enable their connection and interaction. The key idea is that the matchmaking enables, at run time, finding semantic compatibilities among independently defined Web service descriptions. To this end, our approach extends existing methods in order to explain misconnections between Web services. From this we generate Web service compositions that realize the goal, satisfying and optimizing the semantic connections between Web services. Moreover a process of relaxing the hard constraints is introduced in case the composition process failed. Our system is implemented and interacting with Web services dedicated on a Telecom scenario. The preliminary evaluation results showed high efficiency and effectiven...