Increasingly, models are starting to become commonplace and Model Driven Engineering (MDE) is gaining acceptance in many domains including automotive, aerospace, railways, telecommunications, business, and financial organizations.

Over the last years, several modelling platforms have been developed to simplify and automate many steps of MDE processes. However, still several challenges have to be solved in order to enable a wider adoption of MDE technologies. One of the most important impediments in adopting MDE tools is related to the reduced flexibility of existing modelling platforms that do not permit applied development process. For instance, EMF does not permit to enter models which are not conforming to a metamodel: on one hand it allows only valid models to be defined, on the other hand it makes the corresponding pragmatics more difficult. In this respect, there is a wide range of equally useful artefacts between the following extremes:

• - diagrams informally sketched on paper with a pencil
• - models entered in a given format into a generic modeling platform, e.g., Ecore/EMF

At the moment, modelling platforms encompasses only the latter possibility. However, while depending on the stage of the process it makes sense to start with something closer to the former (to promote communication among stakeholders) to eventually end up with the latter (to allow automatic model processing and code generation). Thus, we are interested in exploring the possible forms of flexibility that are required when applying MDE processes, ranging from agile ways to develop modelling artefacts and languages to their flexible in concrete application domains.

Flexibility is also needed to enable wider possibilities for reusing MDE artefacts, like model transformations and code generators. In particular, to deal with the growing complexity of software systems, it is necessary to enforce consistent reuse and leverage the interconnection of the modelling artefacts that are produced and consumed during the different phases of the applied development processes. In such contexts, modularization mechanisms have to be devised in order to enable the development of complex modelling artefacts from smaller ones, which are easier to process and reuse.