[Standards] XEP-0073: Question about service discovery

Peter Saint-Andre stpeter at jabber.org
Wed Feb 7 18:03:09 UTC 2007

Robin Redeker wrote:
> On Wed, Feb 07, 2007 at 03:50:56PM +0100, Remko Tronçon wrote:
>>> Then what are service discoveries (XEP-0030) and entity capabilities
>>> (XEP-0115) for? I would assume that the other client does not support
>>> anything beyond RFC3921 if it doesn't implement XEP-0115.
>> Service discovery was initially only done on specific occasions, and
>> almost exclusively on request of the user. 
> [.snip.]
> Then this might needs some notice in XEP-0030. As I currently
> read it there is nothing that says: "You should not send disco#info
> requests to all contacts when logging in or a contact becomes available."
> Same applies to XEP-0092. If jabber:iq:version-flooding of all contacts
> is discuraged it should maybe contain a note about that. Or XEP-0092
> should be deprecated and superseded by XEP-0115.

I think iq:version should be deprecated for determining the identity of 
entities from which you receive presence (e.g., other users and some 
kinds of gateways). It can still be useful for determining the identity 
of an entity from which you do not receive presence (e.g., servers and 
many kinds of components).

> But for that, the information distributed by the mechanisms in XEP-0115
> should propably also contain the operating system. I'm not sure whether
> XEP-0115 already contains this information.
>> It became clear that you want have the information from disco#info
>> available for all your contacts at all time (amongst others to make
>> better UIs), but it is unreasonable to query each one of your contacts
>> every time you or your contact logs on. This is why XEP-0115 is there:
>> it describes a way to cache disco#info from  everybody, such that you
>> have the information when you need it, and don't need to query it
>> explicitly anymore when you need it.
> Yes, XEP-0115 allows caching of some information. Thats indeed great!
> But XEP-0030 disco#info requests are differnt from the ones in XEP-0115.
> See XEP-0030:
>    <iq type='get'
>     from='romeo at montague.net/orchard'
>     to='plays.shakespeare.lit'
>     id='info1'>
>         <query xmlns='http://jabber.org/protocol/disco#info'/>
>    </iq>
> But the requests in XEP-0115 are using only specific nodes, for example:
>    <iq type='get' to='randomuser1 at capulet.com/resource'>
>      <query xmlns='http://jabber.org/protocol/disco#info'
>             node='http://exodus.jabberstudio.org/caps#0.9'/>
>    </iq>
> Is the information returned by the first one as the information returned by the
> second one? 


> I guess not. 

Why do you guess not?

> XEP-0115 does only allow caching of disco#info requests
> to these nodes, but not of disco requests without a node attribute.
> Are you sure that clients only want the information they can get via XEP-0115?
> And not other information from a XEP-0030 disco#info request?

No difference.


Peter Saint-Andre
XMPP Standards Foundation

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