Evolution of modelling languages

In model-driven engineering, evolution is inevitable over the course of the complete life cycle of complex software-intensive systems and more importantly of entire product families. Not only instance models, but also entire modelling languages are subject to change. This is in particular true for domain-specific languages. Up to this day, modelling languages are evolved manually, with tedious and error-prone migration of for example instance models as a result. This position paper discusses the different evolution scenarios for various kinds of modelling artifacts, such as instance models, meta-models and transformation models. Subsequently, evolution is de-composed into four primitive scenarios such that all possible evolutions can be covered. We suggest that our structured approach will enable the design of (semi-)automatic model evolution solutions.