Designing a DSML implies binding the syntactical concepts of the problem domain with the semantics of a solution domain. Previous work presented a formal framework for language composition where language syntactical patterns (expressed by metamodels) along with their semantics (expressed by transformation models) are combined as small reusable building blocks in a constructive manner, in order to achieve the desired expressiveness for DSMLs. This article refines the framework, as well as showing its application through a case study led in collaboration with CERN (European Organization for Nuclear Research).