Model synchronisation: definitions for round-trip engineering

In a model-centric software development environment, a multitude of different models are used to describe a software system on different abstraction layers and from different perspectives. Following the MDA vision, model transformation is used to support the gradual refinement from abstract models into more concrete models. However, target models do not stay untouched but may be changed due to maintenance work or evolution of the software. Therefore, in order to preserve a coherent description of the whole system, it is necessary to propagate certain changes to a target model back to the source model. However, as transformations in general are partial and not injective, they cannot be easily reversed to propagate changes. This paper presents a formal definition of round-trip engineering and the semantics of target changes in the context of partial and non-injective transformations.