For web-services to become pructdcal, an infrustructure needs to be supported that allows users and applications to discover, deploy, compose, and synthesize services automatically. This automation can take place only if a formal description of the web-services is available. In this paper we present an infrastructure using USDL (Universal Service-Semantics Description Language), a language for formally describing the semantics of web-services. USDL is based on the Web Ontology Language (OWL) and employs WordNet as a common basis for understanding the meaning of services. USDL can be regarded as formal service documentation that will allow sophisticated conceptual modeling and searching of available web-services, automated service composition, and other forms of automated service integration. A theory of safe service substitution for USDL is presented and proved sound and complete. The rationale behind the design of USDL along with its formal specification in OWL is presented with examples. We also compare USDL with other approaches like 0WL-S and WSML and show that USDL is complementary to these approaches.