The semantic Web promises to bring automation to the areas of Web service selection, discovery, composition, invocation. In this paper we introduce a means of facilitating automation of Web service composition by exploiting semantic matchmaking between Web service parameters (i.e., outputs and inputs) to enable their connections and interactions. The idea is that matchmaking functions are key components to find semantic compatibilities among independently Web service descriptions. To this end, our approach extends existing methods (Exact, Plug-in, Subsume, Intersection and Fail) with Concept Abduction to provide explanations of misconnections between Web services. From this we generate Web service compositions that realize the goal, discovering and satisfying 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 France Telecom scenario.