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due to a bug, feature, or just plain oddity of JAXB, it isn't good enough
to just check the form of an element and of its schema. If schema 'a'
(default unqualified) has a complex type with an element with a ref= to
schema (b) (default unqualified), JAXB seems to expect to see a
qualifier, anyway.
So, if the element is local to a complex type,
all we care about is the default element form of the schema and the local
form of the element.
If, on the other hand, the element is global,
we might need to compare namespaces.