Metamodels Relaxation for Model Family Support

A model family regroups related models that vary along some dimension such as time or product in (software) product lines. A model family can be captured as a “150% model” that merges the family members, while enabling the extraction of the individual models. However, this 150% model may no longer conform to the original metamodel of the family members. This paper focuses on the evolution of a language’s metamodel to accommodate both the original models and the 150% model. In particular, it aims to define a technique that minimally relaxes the metamodel constraints related to multiplicities of attributes and association ends in order to enable conformance. The paper uses illustrative examples from two modeling languages (UML class diagrams and the Goal-oriented Requirement Language) to describe the problem and to explore potential approaches for metamodel relaxation. While early results are promising, there are important challenges remaining to balance conflicting forces at play, e.g., having a minimal relaxation (such that existing analysis techniques can be easily adapted for the 150% model) and predicting where relaxation is needed in the metamodel Keywords— Conformance; constraint relaxation; evolution; metamodel; model-driven engineering; model family.