Composing Specifications of Event Based Applications

The event based architectural style has been recognized as fostering the development of large-scale and complex systems by loosely coupling their components. It is therefore increasingly deployed in various environments such as middleware for mobile computing, message oriented middleware, integration frameworks, communication standards, and commercial toolkits. The development of applications based on this paradigm is, however, performed in such an ad-hoc manner that it is often difficult to reason about their correctness. This is partly due to the lack of suitable specification and verification techniques. In this paper, we review the existing theory of specifying and verifying such applications, argue that it cannot be applied for the development of large-scale and complex systems, and finally propose a novel approach (LECAP) for the construction of correct event based applications. Our approach is superior to the existing approaches in many respects: 1) we assume a while-parallel language with a synchronization construct, 2) neither a pending event infrastructure nor a consume statement are required, 3) a dynamic (instead of static) binding is assumed, 4) no restriction is made on the number of simultaneous executions of the same program 5) our approach is oriented towards top-down development of systems. The paper also presents two examples for illustrating the approach.