Re: Lamport and toy languages

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

Lawrence Dickson wrote:
> The fact that projects of such complexity more or less
> arrange themselves in occam, while running against a low practical
> complexity ceiling in non-"live object" languages, is in itself an
> answer to Lamport's argument (as quoted).

> It was
> really pretty trivial, and I'm out of touch: but possibly this message
> needs to be got to people like Lamport?

I am just a bit nervous that we (I) am misrepresenting Lamport's views.
He did mention CSP explicitly as a "PPL": a pseudo programming
language, but more or less in passing as a member of a family.
The main force of his argument is that algorithms and programs
should be discussed at the highest level in "pure mathematics".
That seems to mean something like ZF set theory. At the highest
level, I think I agree, although I think I would want to use Z.

And he does use that phrase about "toy languages" in the first article.
But it is far from clear that his context included CSP or occam at
that point.

His argument about composition is more technical and subtle. I am
not sure that I have fully understood: I ran out of time and
did not read the relevant part of the article carefully. 
What he seemed to being saying is that at his level, his version
of "parallel" just becomes /\ (conjunction), and that the
"Act-Stupid" inference rule was well named in that context.

Just how this relates to CSP refinement I am not sure. At first sight,
we do things differently. But we might well analyse a system in
terms of the properties of its component parallel processes in some
cases, and we might be using the same technique at a deeper level.

So let's not set up Lamport as an Aunt Sally. But as Larry says, at
least it has sparked some discussion.

Adrian
-- 
Dr A E Lawrence (from home)
adrian.lawrence@xxxxxxxxxxxxx