"Do identity-constraints resolve to non-declared nodes?"

Hi,

Excuse me for asking this again, but it came in a 'anySimpleType'
related thread and I felt like better give it an other context.

Are identity-constraints allowed to resolve to non-declared nodes,
i.e. if those nodes are processed by skip/lax wildcards with absent
declarations? I don't see a fall-back mechanism to
anySimpleType/anyComplexType for this scenario to be defined in the
spec, so I currently assume those nodes to have no type at all - but I
would appreciate a confirmation on this.

The question arose as Xerces allowed this in version 2.5.2, but does
not any more.

Kasimier