A barred operational semantics for a subset of WS-CDL with time restrictions

Web Services composition provides a way to obtain value-added services by combining several Web Services. WS-CDL (Web Services Choreography Description Language) is a W3C candidate recommendation for the description of peer-to-peer collaborations for the participants in a Web Services composition. However, the semantics of WS-CDL is provided in a textual way, and hence a complete rigorous semantics is lacking. In this paper we focus our attention on the WS-CDL elements related to concurrency, as well as on the collaborations that have timing restrictions associated. We then provide an operational semantics for a relevant subset of WS-CDL, paying special attention to timed collaborations. This operational semantics is based on barred terms, which allow us to capture the current state of the choreography throughout its execution.