A WSDL-based type system for asynchronous WS-BPEL processes

Abstract

We tackle the problem of providing rigorous formal foundations to current software engineering technologies for web services, and especially to WSDL and WS-BPEL, two of the most used XML-based standard languages for web services. We focus on a simplified fragment of WS-BPEL sufficiently expressive to model asynchronous interactions among web services in a network context. We present this language as a process calculus-like formalism, that we call ws-calculus, for which we define an operational semantics and a type system. The semantics provides a precise operational model of programs, while the type system forces a clean programming discipline for integrating collaborating services. We prove that the operational semantics of ws-calculus and the type system are ‘sound’ and apply our approach to some illustrative examples. We expect that our formal development can be used to make the relationship between WS-BPEL programs and the associated WSDL documents precise and to support verification of their conformance

Adding Sessions to BPEL

“…By separating our semantics into two steps, we were able to propose a formal specification of BPEL with control links more concisely than with Petri nets, notably when it comes to capturing the behavior of dead-path elimination. Other work suggests a formalization that takes into account typing of BPEL process with WSDL descriptors [13]. The session types defined in the present paper can model WSDL descriptors, and they add the possibility to model a service's behavior.…”