Re: [Xen-devel] [PATCH v3 COLOPre 16/26] tools/libx{l, c}: add back channel to libxc

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Wed, 2015-07-01 at 13:07 +0100, Ian Jackson wrote:
> Ian Campbell writes ("Re: [Xen-devel] [PATCH v3 COLOPre 16/26] tools/libx{l, 
> c}: add back channel to libxc"):
> > So to restate the question: Why does the current design deviate from the
> > design in the paper, or does the paper not say what we think it says.
> 
> To be clear, I have no problem if the design has changed since the
> paper was written.  I just want:
> 
>  * A clear high-level explanation of the actually-implemented
>    arrangements to exist somewhere
> 
>  * The commit messages, or code, to refer to that explanation
> 
> A description and explanation of the difference from some other
> somewhat different previously-published document is IMO necessary in
> this case because the primary design reference is that
> previously-published document, which does not correspond to the actual
> code.

Also in this case the implementation requires a significant new bit of
functionality (the back channel) which the previously-published design
did not, so knowing what about that design was
wrong/inadequate/impractical is useful so we can see that the new
functionality is justified.

> 
> Having a design document which disagrees with the implementation is
> dangerous because future programmers will look to the design to
> understand what is going on.
> 
> Ian.



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