The analysis of the composition cycle we did above led us to establish what we expect from a language that describes Web Services. The first requirement is that the language supports the description of capabilities of Web Services, or in other words a description of what function the Web Service accomplishes. Furthermore, there should be an algorithm for indexing descriptions and for comparing them to infer whether they describe the same function. The second requirement is that the language allows the specification of the interaction protocol of the provider, but also it should support the specification of the actual consequences of each interaction. Lastly, it should support mapping of abstract information about inputs expected by the provider and outputs generated to a scheme of information transfer that allows the requester and the provider to exchange actual messages. When these requirements are satisfied, it should be possible to construct an infrastructure for Web Services that is centered around a Registry that performs capability matching. Once Web Services find each other, the infrastructure provides sufficient information for them to interact.
DAML-S and the growing infrastructure around it attempts to satisfy all the requirements described above. DAML-S is emerging as a Web Services description language that enriches Web Services descriptions based on WSDL with semantic information from DAML ontologies and the Semantic Web. DAML-S is organized in three modules, the first one is a Profile that describes capabilities of Web Services as well as additional features that help to describe the service. The second module of DAML-S describes the Process Model of the Web Service, specifically it provides a description of the activity of the Web Service provider from which the Web Service requester can derive the interaction protocol and the consequences of each message exchange. The third feature of DAML-S is the Grounding: a description of how abstract information exchanges described in the Process Model is mapped onto actual messages that the provider and the requester exchange.