+ <variable name="ids">
+ <for-each select="//catalog:uri[@name]">
+ <书社:id>
+ <value-of select="@name"/>
+ </书社:id>
+ </for-each>
+ </variable>
+ <variable name="unique-ids">
+ <for-each select="exsl:node-set($ids)/*">
+ <if test="not(preceding-sibling::*[string(.)=string(current())])">
+ <copy-of select="."/>
+ </if>
+ </for-each>
+ </variable>