如何使用XSLT为外部参照元素创建aff/@id和xref/@rid值，并将xref/sup与aff/sub值进行比较？
输入xml：
<contrib-group>
<contrib contrib-type="author">
<name>
<surname>Mochizuki</surname>
<given-names>Taku</given-names>
</name>
<xref ref-type="aff" rid="aff_ "><sup> </sup></xref>
<xref ref-type="aff" rid="aff_ "><sup> </sup></xref>
</contrib>
</contrib-group>
<aff id="aff_ "><sub> </sub>Departments of ...... Yokohama, Japan</aff>
<aff id="aff_ "><sub> </sub>Department of ...... Yokohama, Japan</aff>