Re: High-integrity networking

["Jeffrey R. Carter" <spam.jrcarter.not@acm.nospam.org>]

Maciej Sobczak wrote:
> 
> I understand this, but this approach has some limitations for me.
> First of all, it limits the scope of discussion to Ada only, and every
> non-trivial distributed system I have seen so far is heterogenous in
> the sense of technology coverage.
> I would like to understand the issues in such systems to get a better
> view on the architectural and functional aspects of communication that
> promotes verification and analysis of the whole. As I've already
> pointed, I understand that Ravenscar can be used as a "mental
> template" that can be extrapolated to distributed systems. This is
> perfectly fine. Still, if there is anything that is particularly worth
> reading *in addition*, I'm looking forward to get some pointers.

Ravenscar is also Ada only, so you can't really talk about it in a 
heterogeneous system. I take it you're trying to apply the spirit of 
Ravenscar to heterogeneous distributed systems, but you're pretty much 
on your own there. I'd probably design such a system as a 
distributed/Annex-E Ravenscar system, then try to ensure that the 
non-Ada parts are equivalent to what an Ada implementation would be, and 
that all communications are equivalent to what would take place in a 
fully Annex-E implementation.

> I have already found CSP (Communicating Sequential Processes), which
> is one possible approach, although what I have seen up to now leaves
> some "minor" details in the air, like the startup of the whole system.
> Ravenscar can afford this, because it's the language implementation
> that has to more or less transparently take care of all these issues,
> but heterogenous systems might need some more explicit handling.

CSP was the basic model for Ada-83 tasking: tasks with entries calling 
each other. That scales nicely to one task per computer.

-- 
Jeff Carter
"You cheesy lot of second-hand electric donkey-bottom biters."
Monty Python & the Holy Grail
14