Re: rewriting CSP processes

[A E Lawrence <adrian.lawrence@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>]

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"Campbell, John" wrote:
> 
> Hi All
> 
> I've a CSP question. The words around the mathematics
> talk about "events" being instantaneous transactions that
> are handshaken (both the Roscoe and Schneider books
> use those terms).  In real life, that's not possible.  Handshaking
> protocols don't execute in zero time, and signals don't
> propagate instantly.  Is there anything in the CSP literature
> that deals with this problem?

Hi John,

I gave a fringe talk at CPA-2000 which addressed these problems in a
rather radical way. The real issue above is that CSP is essentially
discrete. If you model the "start" and "end" of a handshake event as
instantaneous events, then I don't see why you should have any problem
in describing the sort of thing that you describe above. And that is the
usual approach.
But if you want to look at the real continuous world, then a more
fundamental problem is that ordinary CSP semantics uses traces which are
sequences of events. No events can be truely simultaneous. This poses a
variety of problems, and also does not fit comfortably with relativity:
events with space-like separation may have different time orders as seen
by different observers, and one can find a particular observer who sees
the events as simultaneous.

I have a way of overcoming all those problems, but it is
work-in-progress.

Adrian
-- 
Dr A E Lawrence (from home)