Re: [hybi] Versioning is a anti-pattern

[Dave Cridland <[e-mail]>]

On Thu Sep  2 19:42:16 2010, Tim Bray wrote:
> Versioning requres you to make all sorts of REALLY HARD choices,  
> and runs
> the risk of imposing really onerous costs on implementors.  Thus,  
> you need
> to be really convinced that there are really significant benefits  
> before you
> embark on this difficult and risky course of action.  -Tim
> 
> 
To put it another way, versioning is for flag days, whereas feature  
negotiation is for, well, negotiating features.

An example of a protocol with both is XMPP. It has a version, which  
is always 1.0. It also has stream features for peer-to-peer feature  
negotiation.

Jabber, its predecessor, had no version - but it also lacked the  
feature negotiation. Essentially, XMPP's version indicates to the  
receiver that it's okay to announce what features you offer.

So in our release protocol, I'd say we SHOULD NOT have a version, but  
we MAY have a static, never to be changed, version.

For now, though, when we're quite likely to want to change our  
feature negotiation mechanisms, we probably MUST have a version.

The key item is not that versions are bad, but that *changing* them  
is.

Dave.
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