MSM is divided between front–ends and back-ends. At the moment, there is just one back-end. On the front-end side, you will find three of them which are as many state machine description languages, with many more possible. For potential language writers, this document contains a description of the interface between front-end and back-end.

The first front-end is an adaptation of the example provided in the MPL book with actions defined as pointers to state or state machine methods. The second one is based on functors. The third, eUML (embedded UML) is an experimental language based on Boost.Proto and Boost.Typeof and hiding most of the metaprogramming to increase readability. Both eUML and the functor front-end also offer a functional library (a bit like Boost.Phoenix) for use as action language (UML defining none).