On Simulating Networks of Parallel Processes
in Which Simultaneous Events May Occur
Some of the problems of simulating discrete
event systems, particularly computer systems, on 
a conventional digital computer are dealt with.  The
systems are assumed to be described as a network 
of interconnected sequential processes.  Briefly reviewed
are the common techniques used to handle such 
simulations when simultaneous events do not occur, can
be ignored, or can be handled by simple priority 
rules.  Following this, the problem of dealing with simultaneous
events in separate processes is introduced. 
 An abstraction of this problem is developed which admits
solution for a majority of commonly encountered
problems.  The technique will either find a method of
simulating the parallel events or report that none 
can be found.  In some of the latter cases it is shown
to be possible to find a solution by extending 
the information available to the solution technique, but
in many cases the technique becomes computationally 
unfeasible when the additional information is provided.
CACM September, 1969
Parnas, D. L.
