The principal axis of my PhD thesis consisted in developing a new process algebra, called MAPA (Multi-Action Process Algebra ). The syntax of this algebra includes only three operations: prefixing , parallel composition , and restriction . The idea to use multi-actions , i.e. actions composed of a set of simultaneous sendings and/or receivings of elementary signals, is not new. However, I have shown that such a process algebra, even though equipped with a limited number of operations, has ``the most general expression power'', in the sense that any recursively enumerable process graph can be described in it, modulo weak bisimulation. Besides, the absence of choice (+) as a primitive operation ensures that the weak bisimulation is a congruence. I have also shown that it is possible to define a variety of different operational semantics (via the SOS rules) for MAPA without changing its semantics at the level of weak bisimulation.
The preliminary version of these results have been published in [Fra95], and the final results with detailed proofs are included in my PhD thesis (Part III) [Fra96].