[virtmach] Definition a virtual machine ?

[Francois-Rene Rideau]

On Wed, Nov 17, 1999 at 05:36:25PM -0000, Stephen Pelc wrote:
> In both SENDIT and OTA, the VM consists of definitions that 
> cover both programming and O/S access. We used a two stack 
> virtual machine derived from Forth with extensions for local 
> frames.
Interesting. Was your VM significantly different from OpenFirmware?
If no, how so? In either case (yes or no), why so?
Oh, and how do you assert issues of correctness/security
with (low-level?) FORTHish mobile code?

I understand that FORTH-like bytecode seems best for deployment
in small systems, and for programming of small systems even in absence
of portability. However, another thing that bugs me is that
since in a terminal system, at least one of the parties (or am I wrong?)
is always a reasonably big (not resource-lacking) trusted system,
why is there a need that the portable code be executed on the tiny terminal?
After all, it is conceivable that the tiny terminal negotiates
the right non-portable compiled version of code to exchange with
the trusted host (that would have a portable version of the code,
compilers for various target hosts, and a cache of compiled versions).
It seems to me that such architecture would cost less (less support
needed in the mobile part), allow for easier support for extensions,
easier servicing of possible bugs. However, it would move responsibilities
as for system reliability, in that you'd have to assert correction
of a bundle chip&compiler, rather than of a bundle chip&interpreter.
That would be a nice way for technical progress to happen, and open
lots of opportunities...

[ "Faré" | VN: Уng-Vû Bân | Join the TUNES project!   http://www.tunes.org/  ]
[ FR: François-René Rideau | TUNES is a Useful, Nevertheless Expedient System ]
[ Reflection&Cybernethics  | Project for  a Free Reflective  Computing System ]
I don't program enough to be called a "programmer", and I don't unprogram
enough to be called a "non-programmer". So I'm a non-non-programmer, which,
in intuitionnistic logic, is not the same as a programmer.