XSD key/keyref beginner question

Question

I\'m trying to implement a very simple XML schema constraint.

The idref attribute on elements of type should only be

Answer 1

Your XML document, as shown, doesn't include a schemaLocation. When an XML document doesn't reference a schema or DTD, it may pass validation simply by being well-formed XML. (This once happened to a co-worker, using a different validator. I think it's a bug that the validator didn't at least give a warning that it was missing a schema or DTD. But I digress.)

Anyway, it should probably be something like:

<?xml version="1.0"?>
<foo
  xmlns="test" <!-- This is bad form, by the way... -->
  xsi:schemaLocation="test /path/to/schema/document"
    <bar id="1" />
    <bar id="2" />
    <batz idref="1" /> <!-- this should succeed because <bar id="1"> exists -->
    <batz idref="3" /> <!-- this should FAIL -->
</foo>

Answer 2

Even with an assigned schema location this will not work in all parsers.

<?xml version="1.0"?>
<foo xmlns="test"   
     xsi:schemaLocation="test test.xsd"  
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <bar id="1" />
    <bar id="2" />
    <batz idref="1" /> <!-- this should succeed because <bar id="1"> exists -->
    <batz idref="3" /> <!-- this should FAIL -->
</foo>

This will validate as well, because the key is not referencing the target namespace.

Changes that need to be made in the XSD are

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
    targetNamespace="test" 
    xmlns:t="test"
    xmlns="test" elementFormDefault="qualified">

And

<xs:key name="ID">
    <xs:selector xpath="./t:bar" />
    <xs:field xpath="@id" />
</xs:key>

<xs:keyref name="IDREF" refer="ID">
    <xs:selector xpath="./t:batz" />
    <xs:field xpath="@idref" />
</xs:keyref>

For a discussion regarding this behaviour see #1545101