Towards projectional editing for model-based SPLs.

Model-based software product lines (MBSPLs) are implemented using various variability mechanisms. These are commonly categorized whether they separate features virtually (e.g., using annotations) or physically (e.g., using modules). Each of these mechanisms comprises advantages and disadvantages regarding MBSPL development, maintenance and analysis. To date, MBSPL developers have to choose upfront which variability mechanism to use, and the chosen mechanism including its drawbacks is bound to the MBSPL's entire lifecycle. In contrast, projectional editing has recently shown very promising potential of making the development of classical SPLs (e.g., implemented in C/C++) more flexible. User-editable projections allow developers to switch fluidly between different variability mechanisms based upon a common internal representation known as variational abstract syntax tree. In this paper, we report on ongoing work on the projectional editing of MBSPLs, which is challenged by a set of additional requirements. We lay the foundation for different editable projections using a common variational abstract syntax graph (vASG) as internal representation. This vASG is used for a fine-grained variability representation of EMOF-based models. We demonstrate the feasibility of our approach by incorporating different variability mechanism projections (150% models and delta modules) and modeling languages (Ecore class diagrams and UML state machines) used in existing MBSPL case studies.