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Re: Part 2: System Structure


From: Bas Wijnen
Subject: Re: Part 2: System Structure
Date: Thu, 25 May 2006 19:13:10 +0200
User-agent: Mutt/1.5.11+cvs20060403

On Thu, May 25, 2006 at 05:54:39PM +0200, Pierre THIERRY wrote:
> > [...] That's what the proposal provides.  Implementing a constructor
> > around it which works identical to constructors in Jonathan's proposal
> > is trival.
> 
> Could you just describe completely your proposal, so that we can check
> if a constructor in it could have the same properties as in Shapiro's
> model?
> 
> Without an extensive description, you can only argue that some
> properties are met, and we can only suspect that they are or not.

Uhm, which parts aren't clear?  I thought I did give a very extensive
description already.  How the constructor is created?  Just like in Jonathan's
model, there's a process which provides the service of starting a new process.
It does this by accepting some capabilities and plugging them into the newly
created process just before starting it.  One of those can be a space bank
capability.  You can check that this is a real constructor through a
meta-constructor if that is desired, in exactly the same way as this can be
done in Jonathan's proposal.  As I said, the constructor doesn't need opaque
storage at all.  It doesn't need kernel support either.  So there is no
difference at all.

The difference between our models is only in how opaque memory is implemented.
In my model, it is a local property, which only works for processes within the
same "environment".  Processes outside that environment will see that the
memory isn't really opaque (or at least they cannot be guaranteed that it is).
In Jonathan's model, opaqueness is a global property, so memory which is
locally made opaque is also opaque outside that locality (such as a sub-Hurd).
I consider that a bug, he considers it a feature. ;-)  I'm still trying to
find out what he thinks this feature provides.

Thanks,
Bas

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