Override a type in a schema

Given an element:

<theirs:foo>

and an XSD for the 'theirs' namespace defining foo as xs:string, how
can I override that definition with my own type?  One way is:

<theirs:foo xsi:type="my_type_for_foo">

Is there a 1.0 way to do it without using xsi:type ?


thanks

-- 
Andrew Welch
http://andrewjwelch.com