In a complexContent restriction, an attribute the restriction redeclares that the
base type marks use="required" may not be made optional or prohibited. Only
attributes explicitly redeclared that also exist in the base are checked; an
omitted attribute is inherited unchanged. The base reference must resolve to the
schema's own target namespace, and the check stands down for a schema that
composes other documents.
The matching fixed-value clause is deliberately not enforced: it requires
comparing the two fixed values in the attribute type's value space, not lexically
(a list-typed fixed value differing only in whitespace is the same value), so a
string comparison wrongly rejects valid schemas. That clause is left for a later
change (a disclosed under-rejection).
XSTS: invalid schemas accepted 394 to 390, no other bucket raised.
Mihaela Mihaljevic
b80e31d562