Generate activity and state machine diagram

[dulezmaj]

Dear all,
I am working on application (or I can see tool) for specification user
requirements.
This tool follows requirement engineering process. To describe this
activities
I use model (different types of model) in any stages or activities of
RE process.
For example at the beginning I create scenario for use case (I have
meta-model for scenario of use case),
transform then scenario into activity diagram or state machine diagram
and generate prototype for that use case. So, I have executable use
case for simulation and validation.

Can anyone work or worked on something that looks like this, or any
know some tool or have some good reference for this.

Thanks a lot
D.Savic