I have defined a simple schema (small 's') using the XML Schema Designer.
Now I want to reference that schema in a new XML file. First of all I can't
work out how to get the 'Data:Reference Schema' menu option to enable. But
then even if I reference the schema by hand, I get the error 'Expected XML
schema root' when switching to Data View, and I don't get any autocomplete
as promised in the documentation.

Can anyone tell me either how to get the Reference Schema menu option to
enable, or what changes I need to make to the schema file to make it acceptable
to the XML Designer?