<Genus ref="ref1" linkType="local" />
but in an instance doc you will probably get:
<Genus ref="ref1" linkType="local" />Xyz</Genus> or even <Genus>Xyz</Genus>
Applications that generate sample docs based on the schema, like oXygen, or parse the schema, like Pywrapper Schema Parser will not treat the element as having a value.
This is probably also the cause that aliases for these elements are missing in the TAPIR Concept Name server at TDWG: http://rs.tdwg.org/tapir/cns/alias.txt
Regards,
Wouter Addink