[Standards-JIG] XHTML-IM content in presence and IQ?

Wed Dec 14 16:59:25 CST 2005

Recently a client developer contacted me off-list about seeing another 
client send XHTML-IM (JEP-0071) content in a presence stanza, I think in 
the <status/> element -- something like this:

<presence>
   <show>xa</show>
   <status>
     <html xmlns='http://jabber.org/protocol/xhtml-im'>
       <body xmlns='http://www.w3.org/1999/xhtml'>
         <p style='font-size:large'>
           I'm <span style='font-style: italic'>really</span>
           far away!
         </p>
       </body>
     </html>
   </status>
</presence>

That seems evil to me, not least because it violates the jabber:client 
schema in RFC 3921, which specifies that <status/> has a datatype of 
xs:string. [1]

I don't think there is any legitimate use for XHTML-IM content in 
presence stanzas, so my preference would be that we change JEP-0071 to 
say that XHTML-IM content SHOULD NOT be included in presence stanzas. 
The Jabber Council discussed this a bit in today's meeting [2] and came 
to the tentative conclusion that SHOULD NOT would be appropriate, but I 
promised to send a message to this list about it so that we can discuss 
it here.

Right now, any use of XHTML-IM content in presence would be very much 
undefined, since JEP-0071 states that the point of XHTML-IM is to 
provide a formatted version of the <body/> element and it is unclear 
what XHTML-IM content would mean in presence. The only thing I can think 
of is that XHTML-IM content could be used to provide a formatted version 
of the <status/> element, like so:

<presence>
   <show>xa</show>
   <status>I'm really far away!</status>
   <html xmlns='http://jabber.org/protocol/xhtml-im'>
     <body xmlns='http://www.w3.org/1999/xhtml'>
       <p style='font-size:large'>
         I'm <span style='font-style: italic'>really</span>
         far away!
       </p>
     </body>
   </html>
</presence>

I don't see much need for that (and it wastes precious presence 
bandwidth), but if we were to allow it (despite the SHOULD NOT), we 
should specify that that's why the XHTML-IM content is being included.

As to XHTML-IM content in IQs, there might be some kind of use cases in 
which an application would want to include formatted text, but 
personally I am not imaginative enough to think of them right now. 
However, defining such usage would be the responsibility of the using 
protocol. So here I think it would be fine to say that XHTML-IM MAY be 
included in IQ stanzas but such usage is undefined in JEP-0071.

Thoughts?

/psa

[1] However, note that right now JEP-0066 has a similar example, which I 
think needs to be removed or changed.

[2] 
http://www.jabber.org/muc-logs/council@conference.jabber.org/2005-12-14.html

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