> <xsl:variable name = "foo" select =
"//aaa/bbb/key('mykey','myval')/fooval"/>
> where key is :
>
> <xsl:key name = "mykey" select = "ccc/ddd" use = "@id"/>
>

It doesn't make much sense. The expression has exactly the same result as

> <xsl:variable name = "foo" select = "key('mykey','myval')/fooval"/>

There are cases where using key() after "/" would make sense to select the
document to be searched, but in this cases all the nodes are in the context
document so it makes no difference.

Michael Kay
Saxonica