[Standards] Entity Capabilities Woes

Daniel Noll daniel at noll.id.au
Thu Mar 15 21:05:21 UTC 2007

On Friday 16 March 2007 06:19, Peter Saint-Andre wrote:
> Remko Tronçon wrote:
> >> Would be the same for most cases - but from protocol point of view : it
> >> need not necessarily be the same.
> >> Hence, we cache it as a tuple of all three and dont assume that it is
> >> same across versions.
> >
> > That's what we do as well. But on the other hand, if you can assume
> > it, you can cache it by a mapping from disco node
> > (http://psi-im.org/caps#0.11, http://psi-im.org/caps#cs) to features,
> > making it even easier to implement (and avoiding even more disco
> > requests).
> Well as my illustrious co-author said, the intent was that ext is stable
> across application versions. If we make that a MUST in the spec then we
> can save more packets. Seems like a good idea to me.

I can sense this causing a headache further down the track.  Some client will 
put in an "ft" feature for file transfer on version 1.0, and then in version 
2.0 they will add Jingle support.  Clients who happen to query version 2.0 
first will cache that "ft" means Jingle FT, and then interesting things will 
happen when they encounter a version 1.0 client.

It seems like it would be easier for everyone (except disk space, which is 
cheap anyway) if it were assumed that ext is completely free of semantics.

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