I would like to learn such a language. Does such a thing exist ? I am not looking for the graphical design kind of thing, but for (machine) parseable textual representation. It must have provisions for synchronised state machines (via messages or tokens or whatever). One way is to write one lex grammar to represent each state machine, with the tokens recognized by lex being the messages, and productions emitting tokens for the 'other' machines besides doing their own work. The tokens need not be strings. More formal than this ? Petri nets ? What else ? Peter -- The Toronto Linux Users Group. Meetings: http://tlug.ss.org TLUG requests: Linux topics, No HTML, wrap text below 80 columns How to UNSUBSCRIBE: http://tlug.ss.org/subscribe.shtml