[XML Schema 1.1] Is vc:facetAvailable only an attribute of xs:element? (Not an attribute of xs:simpleType?)

Hi Folks,

Is xs:facetAvailable and xs:facetUnavailable only an attribute of xs:element? e.g.

<element name="start-time" vc:facetAvailable="xs:assert">
   ...
</element>


Or, can they be an attribute of xs:simpleType? e.g.

<simpleType name="documentType" vc:facetAvailable="xs:assert">
   ...
</simpleType>


The schema-for-schemas (Appendix A) doesn't seem to define any of the VC stuff. Neither does the DTD-for-schemas (Appendix L)

/Roger