  The idea of the Semantic Web is to annotate Web content and services with
computer interpretable descriptions with the aim to automatize many tasks
currently performed by human users. In the context of Web services, one of the
most interesting tasks is their composition. In this paper we formalize this
problem in the framework of a constructive description logic. In particular we
propose a declarative service specification language and a calculus for service
composition. We show by means of an example how this calculus can be used to
define composed Web services and we discuss the problem of automatic service
synthesis.
