Per cvc-identity-constraint.3 / c-fields-xpaths an identity-constraint
(key/unique/keyref) field must evaluate to a node with a simple type: a
simple-typed element, an element with simple content, or an attribute. The
field-cardinality clause (at most one node) was enforced, but the simple-content
clause was not, so a field selecting a complex-content element was wrongly
accepted at instance-validation time.
Add a structural, false-positive-free check: a field whose selected node is an
element carrying element children has complex (element-only or mixed) content and
can never be simple-typed, so it is flagged. A simple-typed or simple-content
element (text only), an empty or text-only node, and an attribute are left alone,
so no valid field is rejected.
This catches W3C XSTS idK012. XSTS invalid-instances-accepted 26 -> 25,
valid-instances-rejected held at 0.
Mihaela Mihaljevic
2419ab43d9