%T Compositions of Concurrent Processes
%A  Mark Burgin,  Marc L. Smith
%E Peter H. Welch,  Jon Kerridge,  Frederick R. M. Barnes
%B Communicating Process Architectures 2006
%X Using the extended model for view\-centric reasoning, EVCR,
   we focus on the many possibilities for concurrent processes
   to be composed. EVCR is an extension of VCR, both models of
   true concurrency; VCR is an extension of CSP, which is based
   on an interleaved semantics for modeling concurrency. VCR,
   like CSP, utilizes traces of instantaneous events, though
   VCR permits recording parallel events to preserve the
   perception of simultaneity by the observer(s). But observed
   simultaneity is a contentious issue, especially for events
   that are supposed to be instantaneous. EVCR addresses this
   issue in two ways. First, events are no longer
   instantaneous; they occur for some duration of time. Second,
   parallel events need not be an all\-or\-nothing proposition;
   it is possible for events to partially overlap in time.
   Thus, EVCR provides a more realistic and appropriate level
   of abstraction for reasoning about concurrent processes.
   With EVCR, we begin to move from observation to the
   specification of concurrency, and the compositions of
   concurrent processes. As one example of specification, we
   introduce a description of I/O\-PAR composition that leads
   to simplified reasoning about composite I/O\-PAR processes.