Trying XPath 2.0 functions in XSLT, transforming didn't work

I wanted to use XPath 2.0's upper-case(BookTitle) function instead of it's equivalent in XPath 1.0 :
  
translate(BookTitle,'ABCDEFGHIJKLMNOPQRSTUVWXYZ','abcdefghijklmnopqrstuvwxyz') function
   
  When I transformed the xml with xslt like this it didn't work when I used the function: upper-case, but it worked when I used the function: translate :
                     <x:transform doc="${xml}" xslt="${xsl}">
                        <x:param name="book_category" value="${param.r}" />
                    </x:transform>
   
  I was reading in a few forum posts (dating back to 2002, 2005) that Xalan does not support XPath2.0 because XPath2.0 is not in it's
Official W3C Recommendation state yet.
   
  Will the implemenation and support for XPath2.0 begin after XPath2.0 is officially released or is it done in parallel?

 		
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