Define, verify, refine : correct composition and transformation of concurrent system semantics

We present a technique to verify user-defined model transformations, in order to step-wise develop formal models of concurrent systems. The main benefit is that the changes applied to a model can be verified in isolation. In particular, the preservation of safety and liveness properties of such a modification can be determined independent of the input model. This is particularly useful for model-driven development approaches, where systems are designed and created by first developing an abstract model, and iteratively modifying this model until it is concrete enough to automatically generate source code from it. Properties that already hold on the initial model and should remain valid throughout the development in later models can be maintained with our tool Refiner, by which the effort of verifying those properties over and over again can be avoided. This paper generalises our earlier results in various ways, removing several restrictions, improving the focus of the verification method on transformations, and introducing the possibility to add completely new components at any time during the development.