Mixins and Extenders for Modular Metamodel Customisation

Metamodelling is a practical yet rigorous formalism for modelling language definition with a metamodel being its pivotal engineering artifact. A multitude of domain-specific modelling languages (DSML) are engineered to cover various modelling domains. Metamodels of such languages evolve over time by introducing changes and extensions and are further customised to suite project-specific needs. While majority of DSML development techniques provide concepts for creating metamodels from scratch, composition concepts for metamodel customisation beyond class inheritance are sought towards more flexibility and reuse. In this paper, we introduce a modular approach for metamodel customisation based on the idea of mixins and extenders. While mixins allow for defining self-contained metamodel modules for reuse, extenders enable non-intrusive composition of such reusable modules on top of existing metamodels. We show how this approach can be applied in a metamodelling tool such as ADOxx and demonstrate its usefulness by customising the BPMN language. The benefit of the modular metamodel customisation is twofold. On the language engineering level, our approach significantly promotes reuse, flexibility and overall efficiency in language definition and customisation. On the modelling level, the approach leverages engineering flexibility to provide custom modelling languages that better suits enterprise modelling needs.