Heterogeneous systems are naturally complex and their design is a tedious process. The modeling of components that constitute such a system mandates the use of different techniques. This gives rise to the problem of methodology integration that is needed to provide a consistent design. In this paper, we propose a meta-model framework that provides such an integration. The semantics of different computational models can be expressed and used together in the Rosetta framework. We use denotational semantics to define unifying semantic domains, which are themselves extended to provide ontologies for models of computation. Interaction relations defined between models are then used to exploit and analyze model integration. We demonstrate our approach by providing applications where different computational models are used together.