Bidirectional Transformations in the Large

The model-driven development of systems involves multiple models, metamodels and transformations, and relationships between them. A bidirectional transformation (bx) is usually defined as a means of maintaining consistency between "two (or more)" models. This includes cases where one model may be generated from one or more others, as well as more complex ("symmetric") cases where models record partially overlapping information. In recent years binary bx, those relating two models, have been extensively studied. Multiary1 bx, those relating more than two models, have received less attention. In this paper we consider how a multiary consistency relation may be defined in terms of binary consistency relations, and how consistency restoration may be carried out on a network of models and relationships between them. We relate this to megamodelling and discuss further research that is needed.