Compiling heterarchical programs by means of Petri nets

Abstract

We present a method for compiling a program which does not have a conventional tree-like hierarchy of control. Such a structure can arise quite naturally in applications which are strongly user-interactive or contain significant elements of transaction processing, dynamic modelling or process control. Having a heterarchical structure, the application program is capable of being executed simultaneously at an unlimited number of points. Thus a program involving parallel distributed processing, interleaving between processors or multithreading might take advantage of this approach. The encompassing execution strategy is based on the idea of tokens moving through a variant of a Petri net under the control of a firing protocol. We describe an approach to modelling control structures with Petri net semantics and means taken to provide complete reactivation control at run time.