[cap-talk] Is "Authority" Subjective?

[Toby Murray]

On Sun, 2007-06-24 at 21:29 +0100, David Hopwood wrote:
> David Wagner wrote:
> > Toby Murray writes:
> >> Suppose we have a system represented as the following CSP process:
> >>
> >> P = a1 -> a2 -> b -> STOP [] 
> >>     b -> STOP
> >
> > If yes, my concern with this framework is that the non-determinism
> > in the CSP process P conflates several different kinds of choices or
> > several different sources of non-determinism:
> 
> In CSP as conventionally interpreted, P has no nondeterminism. It is
> a process with deterministic behaviour depending on the environment it
> is placed in. There is a separate operator ⊓ (U+2293 SQUARE CAP), that
> introduces nondeterminism and is quite different from [] (choice).
> It sounds as though Toby may be using a different interpretation,
> but I don't understand precisely what the difference is.

No. I was using precisely that interpretation that [] is external
(deterministic) choice. Both Alice and Bob can perform their actions
initially. Whoever performs first gets in. But before one of them has
performed their action, the system will refuse neither.

With a nondet choice, it could be the case the system will refuse a1
even before b has been performed, and vice versa.