ASPECT-ORIENTED CONSTRAINT MANAGEMENT IN METAMODEL-BASED MODEL TRANSFORMATION STEPS

A widely applied approach to model transformation uses graph rewriting as the underlying transformation technique. In case of diagrammatic languages, such as the Unified Modeling Language (UML), the exclusive topological matching is found to be not enough. To define the transformation steps precisely beyond the structure of the visual models, additional constraints must be specified which ensures the correctness of the attributes, or other properties to be enforced. Dealing with OCL constraints provides a solution for these unsolved issues. The use of OCL as a constraint and query language in modelling is essential. We have shown that it can be applied to model transformations as well. Often, the same constraint is repetitiously applied in many different places in a transformation. It would be beneficial to describe a common constraint in a modular manner, and to mark the places where it is to be applied. This paper discusses (i) the problem of crosscutting constraints in visual model transformation steps, and provides an aspect-oriented solution for a consistent constraint management. It introduces the concepts of aspect-oriented constraints and a new type of aspect, the constraint aspects. (ii) In general, it is difficult to require a whole transformation to validate, preserve or guarantee certain properties because transformations are built form isolated transformation steps ordered by a control structure. This problem is solved by the provided constraint weaver methods, which weave the constraints into the model transformation steps prior to the execution. (iii) Furthermore, the work presents offline constraint optimization (normalization) algorithms, which are part of the presented weaving process