Abstract. Many model transformation languages of different nature have been proposed during the last years, each one of them suitable for a certain kind of transformation task. However, a complex transformation problem may not fall into a single transformation category, making the solution written in the chosen transformation language suboptimal, as some concerns cannot be handled naturally. To tackle this issue, we propose to define a model transformation tool as a family of model transformation languages. Each member of the family is a simple language intended to deal with a particular kind of transformation task. In this paper we discuss the different issues involved, such as design decisions, interoperability among languages, and composability. We illustrate the paper with a transformation from UML and OCL to Java, in which languages for pattern matching, mapping, attribution and target-oriented transformations are used. Finally, the approach is validated with a proof-of-concept implementation
