Model-Based Design of complex software systems is an activity that requires the use of different modeling formalisms, with different perspectives of the system, to cover all relevant aspects of the system, to avoid over-design, to employ manageable models and to support system integration The comprehensive use of models in design has created a set of challenges beyond those of supporting one isolated design task In particular, the need to combine, couple, and integrate models at different levels of abstraction and in different formalisms is posing a set of specific problems that must be tac