Achieving Fault Tolerance by a Formally Validated Interaction Policy

This paper addresses the rigorous validation of an integrity policy by means of the application of formal methods and related support tools. We show how the policy, which provides a flexible fault tolerant schema, can be specified using a process algebra and verified using model checking techniques. Actually, we show how this approach allows both the generic validation of a middleware based on such integrity policy, and the validation of an integrated application which internally uses this mechanism. In the first case, the fault tolerance of a system, possibly composed of Commercial Off The Shelf (COTS) components, is guaranteed by a validated resident interaction control middleware. The second case applies instead when the application is forced to use a given middleware, as it is the case of Web Services.