<schema xmlns:my='my.ns/'

       xmlns='http://www.w3.org/2001/XMLSchema'
       targetNamespace='http://my.ns/'
       >
<attribute name='other' type='string'/>
<element name='my'>
  <complexType>
    <simpleContent>
      <extension base='string'>
        <attribute ref='my:other'/>
      </extension>
    </simpleContent>
  </complexType>
</element>

</schema>