In Semantic Web technologies, searching for a service means to identify components that can potentially satisfy the user needs in terms of outputs and effects (discovery), and that, when invoked by the customer, can fruitfully interact with her (contracting). In this paper, we present an application framework that encompasses both the discovery and the contracting steps, in a unified search process. In particular, we accommodate service discovery by ontology-based reasoning, and contracting by automated reasoning about policies published in a formal language. To this purpose, we consider a formal approach grounded on Computational Logic, and Abductive Logic Programming in particular. We propose a framework, called SCIFF Reasoning Engine, able to establish, by ontological and abductive reasoning, if a semantic web service and a requester can fruitfully inter-operate, taking as input the behavioral interfaces of both the participants, and producing as output a sort of a contract.