ma.
 This schema is assumed to match what would be otherwise produced
 by the schema generator (same element names, same type names...)

 <p>
 This feature is intended to be used when a set of the Java classes
 is originally generated from an existing schema, hand-written to
 match externally defined schema, or the generated schema is modified
 manually.

 <p>
 Value could be any absolute URI, like <code>http://example.org/some.xsd</code>.
 It is also possible to specify the empty string, to indicate
 that 