[xsl] counting and grouping issue

["Charles Ohana" <charles.ohana@xxxxxxxxxxxxxx>]

Hello,
I'm having an issue while counting and aggregating nodes that have similar 
subnodes value within the same category.
In other words I'm trying to do something like a group by (in sql)
I must be doing something wrong somewhere. Please see my xml, stylesheet 
and output to see what I'am trying to accomplish.

Thank you all 4 ur help.

OUTPUT
ONE : 4 : Gary Numan : Are Friends Electric
ONE : 4 : Gary Numan : We Are Glass
ONE : 4 : Gary Numan : I Die You Die
TWO : 4 : Gary Numan : Unknown
TWO : 1 : Bob MArley : Jammin

EXPECTED OUTPUT
ONE : 3 : Gary Numan : Are Friends Electric
ONE : 3 : Gary Numan : We Are Glass
ONE : 3 : Gary Numan : I Die You Die
TWO : 1 : Gary Numan : Unknown
TWO : 1 : Bob MArley : Jammin

XML
<?xml version="1.0" encoding="ISO-8859-1" ?>
<ApplicationCatalogue>
  <Category name="category 1" description="ONE">
     <Product code="TT000002630">
        <Attributes>
           <title>Are Friends Electric</title>
           <author>Gary Numan</author>
        </Attributes>
     </Product>
     <Product code="TT000002631">
        <Attributes>
           <title>We Are Glass</title>
           <author>Gary Numan</author>
        </Attributes>
     </Product>
     <Product code="TT000002632">
        <Attributes>
           <title>I Die You Die</title>
           <author>Gary Numan</author>
        </Attributes>
     </Product>
  </Category>

  <Category name="category 2" description="TWO">
     <Product code="TT000002632">
        <Attributes>
           <title>Unknown</title>
           <author>Gary Numan</author>
        </Attributes>
     </Product>

     <Product code="TT000002669">
        <Attributes>
           <title>Jammin</title>
           <author>Bob Marley</author>
        </Attributes>
     </Product>
  </Category>
</ApplicationCatalogue>


XSL
<xsl:transform version="1.0" 
xmlns:xsl="http://www.w3.org/1999/XSL/Transform";>
  <xsl:output method="text" indent="no"/>
     <xsl:key name="itemsByAuthor" match="Product" 
use="Attributes/author"/>
     <xsl:template match="/ApplicationCatalogue">
        <xsl:for-each select="Category">
        <xsl:for-each 
select="Product/Attributes/author[not(.=preceding::Product/Attributes/author)]">
            <xsl:variable name="cnt"><xsl:value-of 
select="count(key('itemsByAuthor', .))" /></xsl:variable>
                <xsl:for-each select="key('itemsByAuthor', .)">
                    <xsl:value-of select="../@description" />
                    <xsl:text> : </xsl:text>
                    <xsl:value-of select="$cnt" />
                    <xsl:text> : </xsl:text>
                    <xsl:value-of select="Attributes/author" />
                    <xsl:text> : </xsl:text>
                    <xsl:value-of select="Attributes/title"/>
                    <xsl:text>&#10;</xsl:text>
                </xsl:for-each>
        </xsl:for-each>
        </xsl:for-each>
     </xsl:template>
</xsl:transform>