RE: giving key() a context (changes between XSLT 1.0 a

>     ...
>     <xsl:variable name='auth' select='$biogs/key("biog", $name)'/>
>     ...
> 
>  </xsl:template>
> 
> That is, key() is used directly in the expression, and has its
> context supplied by the previous expression step.  Assuming I'm
> understanding all this correctly, then I like this approach more than
> the three arg key() call, because it seems to fit better with
> typical XSLT usage patterns.

There is actually one use case where the 3-argument approach is much more
convenient, namely when the second argument is a node in a different
document from the one you want to search:

select="key('k', @code, document('codes.xml'))"
> 
> The above, however, didn't work in my XSLT 1.0 processor.  No
> surprise, I guess.  No need for the for-each hack if you could do
> that.  But I've been looking around for a succint explaination of
> what exactly changed in XSLT 2.0 to make this possible, and I haven't
> been able to find it yet.

The change was actually in XPath 2.0, which now allows any expression on the
rhs of the "/" operator. XPath 1.0 restricted this to be an axis step.  
> 
> So I guess my questions are:
> 
>  * is it true that the above ($biogs/key( ...)) really is illegal in
>    XSLT 1.0?

Yes.
> 
>  * what restriction was relaxed to make this possible in XSLT 2.0?
> 

See above.

Michael Kay