Dynamic composition of web services requires an automated step of contracting, i.e., the computation of a possibly fruitful interaction between two (or more) services, based on their policies and goals. In previous work, the SCIFF abductive logic language was used to represent the services' policies, and the associated proof procedure to perform the contracting. In this paper, we build on that work in order to exploit the results of the Description Logics research area to represent domain specific knowledge, either by importing the knowledge encoded in an ontology into a SCIFF knowledge base, or by interfacing the SCIFF proof procedure to an existing ontological reasoner.