On Modular De nitions and Implementations of Programming Languages

We provide a framework for modular deenitions and implementations of programming language based on abstract state machines. It is based on composition mechanism of state transition systems. State transition systems abstract from the algebraic structure of the states of an abstract state machine and focus on the behavior of state transitions. Implementations are based of reenements of state transition systems. We show that it is possible to compositionally reene state transition systems. Parameterized state transition systems consider the composition as an operator (similar to e.g. C++-templates). Again, it turns out that reene-ment of parameterized state transition systems is compositional. These techniques are then specialized to abstract state machines and programming language deenitions. It turns out that Montages can viewed as a set of parameterized abstract state machines.