  This paper presents ongoing research on the application of PSF in the field
of software engineering and reengineering. We build a new implementation for
the simulator of the PSF Toolkit starting from the specification in PSF of the
architecture of a simple simulator and extend it with features to obtain the
architecture of a full simulator. We apply refining and constraining techniques
on the specification of the architecture to obtain a specification low enough
to build an implementation from.
