System modeling is a widely used technique to model state-based systems. System models are often used during the development of a software system, e.g., in partial code generation and in test generation. Several modeling languages have been developed to model state-based software systems, e.g., EFSM, SDL, and state charts. Although state-based modeling is very useful, system models are usually large and complex, and they are frequently modified because of specification changes. Identifying the effect of these changes on the model and consequently on the underlying system is usually challenging and time-consuming.