[Standards] PubSub (XEP-0060) Node Discovery and Service Delegation (XEP-0291)

Dave Cridland dave at cridland.net
Wed Nov 30 20:35:04 UTC 2011


On Wed Nov 30 19:27:26 2011, João Miguel Gonçalves wrote:
> In one of the scenarios we need to find a PubSub (XEP-0060) service  
> (component JID) and node based on some metadata. Example: we want  
> to find where user me at jmgoncalv.es<mailto:me at jmgoncalv.es>  
> publishes his http://jabber.org/protocol/tune information.

The thing is, this is basically what PEP is for.

>  We are not using PEP, and this would potentially be extended to  
> discover where the user publishes any information based on some  
> namespace with associated semantics.


And the whole point of PEP was to provide this discoverability in a  
simple, clean manner. And even better than that, it works, very  
effectively. This is your solution.

> Can someone point me to some spec I missed, that might be of  
> interest?
> What is the take on XEP-0291? Would you see it fulfilling this use  
> case?

So in your example case, extending XEP-0291 to use as a fallback is  
reasonable.

But don't fool yourself - it is a fallback, and it's vastly less  
efficient. In addition, users all need to use the same registry, and  
need this to be configured in non-trivial ways.

The vast majority of modern servers can do what you need in PEP;  
design for that case. The most obvious example of a service which  
doesn't yet do PEP is Google, but I'm confident that they would  
implement PEP in a flash if there was a killer app - or just a clear  
demand. Meanwhile, you have XEP-0291 as a fallback.

Dave.
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