Towards a Model-Based Refinement Process for Contractual State Machines

We present a rigorous model-based approach to the stepwise design of contractual state machines, which are a simplified form of state charts extended with declarative specifications. The approach is based on application of a set of refinement patterns, that can be validated against a formal semantics, and that are implemented using update-in-place model transformations. We describe the integrated tool support we are implementing for this model-based approach, and illustrate the approach with small examples.