[Standards-JIG] JEP 60: Most Recent Items defined?

Chris Mullins chris.mullins at coversant.net
Fri May 20 22:32:49 UTC 2005


[Requiring Document Order parsing for Node Items]

PSa Wrote:

> Well, if the JEP specifies this, then it specifies how an 
> implementation must parse XML nodes, and that seems problematic 
> to me -- especially since it is possible that the order of 
> child elements could be changed en route (e.g., by an 
> intermediate router).

Defining the node 'age' as being in Document Order seems a fairly
reasonable requirement. DOM preserves this, SAX preserves this, and all
sorts of things (such as XPath) require it to be preserved. So while it
could be changed by a router in the middle, it's pretty unlikely.

Alternativly, if multiple items are being published at once, we could
require an age attribute:
<iq [...]>
    <pubsub xmlns="http://jabber.org/protocol/pubsub">
        <publish node="somenode">

            <item id="left" age="1">
                <leftnode/>                 
            </item>

            <item id="right" age="2">
                <rightnode/>
            </item>
        </publish>
    </pubsub>
</iq>

I don't particularly like this, but it would solve the problem. 


> Naturally the compliance test could simply say that the concept 
> of "most recent item" is ambiguous in these cases, no?

Except that it will frustrate clients as well as compliance tests. A
customer may build an implementation on top of a specific pubsub
implementation, and then be unable to switch to a different
implementation due to this. 

-- 
Chris Mullins



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