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].