Towards a Formal Specification of an Electronic Payment System in CSP-CASL

This paper describes the formal specification of a future banking system by abstract data types and process algebra. In contrast to previous exercises (e.g., [1]), the system's description is an actual industrial standard which is being used to develop the next generation of automatic banking machines. The specification language CSP-CASL is particularly well suited to this type of problem, since it combines both control and data aspects and allows loose specification of data types for later refinement. During the formalisation, several inconsistencies and ambiguities were exhibited. The obtained specification serves as a starting point for further validation.