Re: [vwrap] Statements of Consensus. Flexibity First.

Boroondas Gupte <> Wed, 30 March 2011 11:28 UTC

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Date: Wed, 30 Mar 2011 13:29:56 +0200
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Subject: Re: [vwrap] Statements of Consensus. Flexibity First.
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On 03/30/2011 03:14 AM, Carlo Wood wrote:
> Perhaps we should also start a wiki page (it's nice
> to have a stable url that one can refer to, which still
> is editable; that give me at least a feeling of progress),
> about statements that we reached consensus over.
Good idea.

> Being an abstract thinker and analyst, I believe we
> can tackle many of the current discussions at a much
> higer abstraction level first, making it easier, or
> even possible, to deal with the more detailed points
> of discussion.
We'll probably have to switch back and forth between levels of
abstraction during the discussion. A pure top-down design often won't
work. But I feel it's indeed reasonable to start at a higher abstraction
and see where we can go from there.

> I'd like to start with one such statement and ask
> for consensus on it (and if not, give your rationale
> why not).
> * Whenever a change X in the protocol is proposed
>   (which might be an addition, a change of existing
>   protocol or even deletion: any change, making
>   the protocol (VWRAP) go from A --> B), then that
>   change is accepted as part of VWRAP provided that:
Formulated like this, it sounds like the following requirements together
would be sufficient for acceptance. I guess you rather wanted to express
that they should be necessary for acceptance, but might not be
sufficient (further requirements might apply).

>   1) Protocol B can do everything that A could do.
>   2) No substantial extra demands are being made on
>      an implementation that only implements the
>      functionality of A.
As necessary but not sufficient acceptance requirements, I can consent
to these. I cannot consent to them as sufficient acceptance requirements.

> In other words: we choose for flexibility.
Or more specifically, total backwards compatibility between versions of
VWRAP. However, to make it easy (or at least easier/possible) to design
changes X or new versions B, such that they fulfill these backwards
compatibility requirements, we should already design previous versions A
for "forward compatibility".

If I remember correctly, you have made suggestions in past messages on
how to achieve such forward compatibility (e.g. protocol versioning
combined with protocol negotiation).

> Under no circumstances we want the *protocol* itself
> to be a limitation in what is possible, when that
> extra flexibility/possibility doesn't cost much for
> those not needing or using it.