CSPP and Event Priority

摘要

CSPP is an extension of CSP which includes priority as used in standard Occam. The Occam community has often discussed whether those notions are really adequate, a particular concern being the difficulties associated with priority inversion. One idea is to give priority to sets of events considered independently of the processes that perform them. We call this event priority. Event priority is static in this presentation. But it is possible to handle dynamic priority using a global synchronisation when the event priority changes. Obviously there is no problem for a software system with a central scheduler, but the theory here is addressing a far wider class of systems, in particular massively parallel, widely distributed, implemented in either hardware or software or both. It may be that some higher level of abstraction should replace priority: priority is a mechanism for achieving certain properties, often relating to time and limited resources. Here we content ourselves with finding a formal description of a language including event-priority.