Abstract
The semantic web vision will facilitate automation of many tasks, including the location and dynamic reconfiguration of web services. In this article, we are concerned with a specific stage of web service location, called, by some authors, contracting. We address contracting both at the operational level and at the semantic level. We present a framework encompassing communication and reasoning, in which web services exchange and evaluate goals and policies. Policies represent behavioural interfaces. The reasoning procedure at the core of the framework is based on the abductive logic programming SCIFF proof-procedure. We describe the framework, show by examples how to formalise policies in the declarative language of SCIFF, and give the framework a model-theoretic and a sound proof-theoretic semantic