Over the last years, Model Driven Engineering platforms evolved from fixed metamodel tools to systems with variable metamodels. This enables dealing with a variety of Domain Specific Languages (DSLs). These generic platforms are increasingly adopted to solve problems like code generation. However, these environments are often limited to syntax definitions. The AMMA platform conceives DSLs as collections of coordinated models defined using a set of core DSLs. For broadening the approach to semantics definition, AMMA should thus be extended. The paper presents an extension of the core DSLs of AMMA to specify the dynamic semantics of a range of DSLs by means of Abstract State Machines. Thus, DSLs can be defined not only according to their abstract and concrete syntaxes but also to their semantics in a uniform and systematic way. The approach is validated by means of the semantic bootstrap of the ATL transformation language.