[standards-jig] Some thoughts on JEP0030 Service Discovery

DJ Adams dj.adams at pobox.com
Mon May 20 09:59:02 CDT 2002


Hi all

well, I finally got round to reading 0030 Service Discovery. I had a 
few thoughts, some of which I've already discussed in part with Ryan,
but I thought it was worth noting them down here:

Inflexibility?
--------------
1.1. "The protocol is not easily extensible...categories and subcategories
...explicitly defined as the only valid categories"

I'd take issue with this; as far as I understand it, an explicit provision
in the form of the 'x-' prefix was made in iq:browse for subcategories. So
iq:browse isn't as inflexible as this section of 0030 might suggest.


Discovery vs Navigation
-----------------------
1. "To address these shortcomings...new protocol that is intended to 
supersede jabber:iq:browse".

Now this is really just wording and / or semantics, but I think it's
important to stress (or not lose sight of the fact that) iq:browse isn't
just service discovery. It's a generic way of navigating hierarchies of
entities (things with JID addresses). While 'browse' suggests navigation,
'disco' suggests discovery. So neither is totally accurate, or can be. 
Perhaps it's just worth putting in a note that iq:disco intends to 
support all the uses of iq:browse (discovery, navigation, etc).


IRC Channel List example
------------------------
The 'what IRC channels are there' example use of browse was rightly 
cited as an instance where too much data comes back down the pipe as
a result. But it's not obvious where the problem lies, and how iq:disco
might address it.

Too much for the computer? - how about support for an iq:search style
multi-packet result (iq-set...iq-set...iq-result)?

Too much for the human? - well, assuming the implicit answer is to use
filters (e.g. <feature type='connection'/> in Example 7), how might that
work in this IRC channel context, or any context where we don't _control_
the metadata? I understand there was some discussion of using a max='n'
attribute in the request, but this would only make sense if it was 
accompanied by a startingfrom='' type mechanism too. And that usually
implies some sort of state. 


Melding with Pubsub
-------------------
In section 4, a brief mention of pubsub is to be found. Is it possible
to have an example of how this might work? Considering the status of
the current proposals, this might sound like a leading question ;-) But
it's not. I just think it would be useful to have an example. 


Well, that's just my 2p as usual

dj



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