Type Checking Choreography Description Language

The Web Services Choreography Description Language (WS-CDL) is a W3C specification developed for the description of peer-to-peer collaborations of participants from a global viewpoint. Currently WS-CDL has no rigorous static type checking. We believe that introducing a type system will exclude many design and description errors, and ensure desirable properties of the choreography specifications. In this paper, we took a core language CDL, which covers most of the important features of the WS-CDL, and is more convenient for the study. We developed the abstract syntax and operational semantics of CDL, and defined a collection of rules which can be used to check if a choreography is well-typed. Moreover, we also proved some type safety theorems for CDL in the sense that well-typed choreography cannot get stuck. We show how the use of type information can allow us to gain confidence in the correctness of a choreography.