Section 3.11.5 of the spec describes how key/keyref information is captured
in the PSVI in the form of an identity-constraint table:
http://www.w3.org/TR/xmlschema-1/#d0e14060
But (a) the authors of the spec clearly don't expect implementations to
expose the information in that form:
The Identity-constraint Binding information item, unlike others in this
specification, is essentially an internal bookkeeping mechanism. It is
introduced to support the definition of Identity-constraint Satisfied
(§3.11.4) above. Accordingly, conformant processors may, but are not
required to, expose them via [identity-constraint table] properties in the
·post-schema-validation infoset·. In other words, the above constraints may
be read as saying ·validation· of identity-constraints proceeds as if such
infoset items existed.
and (b) even if implementations did expose the information, I think it would
be quite hard to make use of it in your application.
Michael Kay
http://www.saxonica.com/
