%T Representation and Implementation of CSP and VCR Traces
%A  Neil C.C. Brown,  Marc L. Smith
%E Peter H. Welch,  S. Stepney,  F.A.C Polack,  Frederick R. M. Barnes,  Alistair A. McEwan,  G. S. Stiles,  Jan F. Broenink,  Adam T. Sampson
%B Communicating Process Architectures 2008
%X Communicating Sequential Processes (CSP) was developed
   around a
formal algebra of processes and a semantics based
   on traces (and
failures and divergences). A trace is a
   record of the events
engaged in by a process. Several
   programming languages use, or
have libraries to use, CSP
   mechanisms to manage their concurrency.
Most of these lack
   the facility to record the trace of a program. A
standard
   trace is a flat list of events but structured trace
models
   are possible that can provide more information such as
the
   independent or concurrent engagement of the process in
   some
of its events. One such trace model is View\-Centric
   Reasoning
(VCR), which offers an additional model of
   tracing, taking into
account the multiple, possibly
   imperfect views of a concurrent
computation. This paper also
   introduces <q>structural</q> traces, a
new type of trace
   that reflects the nested parallelism in a CSP
system. The
   paper describes the automated generation of these
   three
trace types in the Communicating Haskell Processes
   (CHP) library,
using techniques which could easily be
   applied in other libraries
such as JCSP and C++CSP2. The
   ability to present such traces of
a concurrent program
   assists in understanding the behaviour of
real CHP programs
   and for debugging when the trace behaviours are
wrong. These
   ideas and tools promote a deeper understanding of
   the
association between practicalities of real systems
   software and
the underlying CSP formalism.