Towards non-intrusive composition of executable models

An essential operation in model-driven engineering is composition of models and their metamodels. There exist several mechanisms for model composition. However, most of these only consider composition of either models or metamodels and not both kinds of models simultaneously, and do not address how the composition impacts modelling artefacts like editors, transformations and semantics. Moreover, model composition mechanisms typically deal with model structure and do not consider operational semantics. In this paper, we discuss a novel approach for the composition of both models and metamodels in a virtually non-intrusive manner. We achieve this by utilising a placeholder mechanism where classes in one metamodel may represent classes of another. The ideas presented have been validated by the construction of a framework. We will illustrate how non-intrusive composition allows linking the operational semantics of different languages without rendering existing modelling artefacts inconsistent. This increases the flexibility in how languages can be combined, and reduces the amount of necessary changes of tools and other modelling utilities.