The model-driven architecture (MDA) is an approach to model-centric software development. The concepts of models, metamodels, and model transformations are at the core of MDA. Model-driven development (MDD) distinguishes different kinds of models: the computation-independent model (CIM), the platform-independent model (PIM), and the platform-specific model (PSM). Model transformation is the process of converting one model into another model of the same system, preserving some kind of equivalence relation between them. One of the key concepts behind MDD is that models generated during software developments are represented using common metamodeling techniques. In this chapter, we analyze an integration of MDA metamodeling techniques with knowledge developed by the community of formal methods. We describe a rigorous framework that comprises the NEREUS metamodeling notation (open to many other formal languages), a system of transformation rules to bridge the gap between UML/OCL and NEREUS, the definition of MDA-based reusable components, and model/metamodeling transformations. In particular, we show how to integrate NEREUS withalgebraic languages using the Common Algebraic Specification Language (CASL). NEREUS focuses on interoperability of formal languages in MDD.