Implementing Tile Systems : Some Examples from Process

This work reports on some useful applications of the tile model to the speciication and execution of CCS-like process calculi. This activity is part of our ongoing research on the relation between tile logic and rewriting logic. 1 Overview Tile Logic 1;2 is a framework for modular descriptions of the dynamic evolution of concurrent systems, extending rewriting logic 3;4 (in the non-conditional case), by side-eeects and rewriting synchronization. These aspects are very important when modelling process algebras, because they allow us to represent the dynamic interaction between processes and \the rest of the world". Since rewriting logic is the semantic basis of several language implementation eeorts, it is interesting to map tile logic back into rewriting logic in a conservative way, to obtain executable speciications of tile systems. However, as explained in 5 , a correct rewriting implementation of tile logic must deal with two issues, namely the possible identiication of diierent tile proofs, and the development of a meta-layer to control the rewritings. By exploiting the reeective capabilities 6;7 of the language Maude 8 , the meta-layer can be speciied as a kernel of internal strategies 9 , which may help the user to direct the computation and to collect the possible results (Maude is a language that has been recently developed at SRI International, and it is based on rewriting logic). In tile logic, a set of rules combines certain basic modules, which may interact through their interfaces. Roughly speaking, modules are just open (e.g., partially speciied) conngurations of the system. The behaviour of a 1