Hi,

If you want the identifiers to be unique across all reports and targets,
you can add this to your declaration of the Request element:

<xs:key name="uniqueIDs">
  <xs:selector xpath="*"/>
  <xs:field xpath="@identifier"/>
</xs:key>

If you only want the identifiers to be unique among targets (and not
reports) and you know all the target element names in advance, you could
use:

<xs:key name="uniqueIDs">
  <xs:selector xpath="demo:DummyTarget|demo:DummyTarget2"/>
  <xs:field xpath="@identifier"/>
</xs:key>

But, if you only want the identifiers to be unique among targets, and
you don't want to hard code the names in there, I think you'd have to
use a different attribute name for target IDs vs. report IDs.

To enforce the reference, you can use:

<xs:keyref name="validRefs" refer="uniqueIDs">
  <xs:selector xpath=".//demo:TargetReference"/>
  <xs:field xpath="@identifier"/>
</xs:keyref>

Note that I use a "demo" prefix - You would have to map your target
namespace to a prefix in your schema in order for this to work, because
XPath expressions do not take into account default namespace
declarations.

Hope that helps,
Priscilla

----------------------------------
Priscilla Walmsley
Author, Definitive XML Schema
http://www.datypic.com
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