xml-dev - RE: Array content model (more like a collection)

["Arnold, Curt" <Curt.Arnold@hyprotech.com>]

John OSullivan wrote (paraphrased):

Should I do lists of items as:

<purchaseOrder>
	<items>
		<item/>
		<item/>
		<item/>
	</items>
</purchaseOrder>

- or -

<purchaseOrder>
	<item/>
	<item/>
	<item/>
</purchaseOrder>

------------

I think they key issue is whether you anticipate ever
needing to qualify the list of items with additional information
such as "allOrNone", "shipInOrder".  Without an element that
corresponds to the list of items, then you would have to force
that information into the <purchaseOrder> element.

If you wanted to support purchase orders that supported
richer item lists like a list of alternatives (where the 
vendor could ship any one of three 10-ft RJ45 cables depending
on availability), then you might want to create containing 
elements like <sequence>, <all>, <one> (or maybe <choice>) that
could be substituted for <item>, so you could have something like:

<!--  send me the one item  -->
<purchaseOrder>
	<item/>
</purchaseOrder>

<!--  send me all of the listed items  -->
<purchaseOrder>
	<all>
		<item/>
		<item/>
	</all>
</purchaseOrder>

<!--  send me one of the two listed items  -->
<purchaseOrder>
	<!--   one o
	<one>
		<item/>
		<item/>
	</one>
</purchaseOrder>

<!--  send me either the first two items 
	(maybe a flashlight and a package of batteries)
      or the third item (flashlight set that comes with batteries)  -->
<purchaseOrder>
	<one>
		<all>
			<item/>
			<item/>
		</all>
		<item/>
	</one>
</purchaseOrder>

Again, the design depends on the nature of your requirements.

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