'Sort' One XML file into another XML file? (Help required pls!)

[TooMuch2AM]

In need of some good advice on 'consolidating' an XML file into another folks. Hope you can help!

My souce XML looks like so:

<?xml version="1.0" encoding="utf-8"?>
<vehicles>
    <make xmake="ALFA ROMEO">
        <model xmodel="159 SPORTWAGON">
            <derivative xderivative="3.2 V6 JTS Q4 Lusso 5dr" />
        </model>
    </make>
    <make xmake="ALFA ROMEO">
        <model xmodel="SPIDER CONVERTIBLE">
            <derivative xderivative="3.2 V6 JTS Q4 2dr" />
        </model>
    </make>
    <make xmake="ALFA ROMEO">
        <model xmodel="SPIDER CONVERTIBLE">
            <derivative xderivative="2.8 V6 Q4 2dr" />
        </model>
    </make>
    <make xmake="CITROEN">
        <model xmodel="C4 COUPE SPECIAL EDITIONS">
            <derivative xderivative="1.6HDi 16V by LOEB 3dr" />
        </model>
    </make>
    <make xmake="FORD">
        <model xmodel="S-MAX DIESEL ESTATE">
            <derivative xderivative="2.0 TDCi LX 5dr" />
        </model>
    </make>
</vehicles>

Basically I have several vehicles but need to group them by Make, Model and Derivative thus:

<vehicles>
                <make name='ALFA ROMEO'>
                                <model name='159 SPORTWAGON'>
                                <Derivative>3.2 V6 JTS Q4 Lusso 5dr</Derivative>
                                </model>
                                <model name='SPIDER CONVERTIBLE'>
                                                <Derivative>3.2 V6 JTS Q4 2dr</Derivative>
                                                <Derivative>2.8 V6 Q4 2dr</Derivative>
                                </model>
                </make>
               
                <make name='CITROEN'>
                                <model name='C4 COUPE SPECIAL EDITIONS'>
                                                <Derivative>1.6HDi 16V by LOEB 3dr</Derivative>
                                </model>
                </make>
               
                <make name='FORD'>
                                <model name='S-MAX DIESEL ESTATE'>
                                                <Derivative>2.0 TDCi LX 5dr</Derivative>
                                </model>
                </make>
</vehicles>

I'm pretty new to using XSL so any pointers towards how to acheive this would be gratefully received!

Many thanks!
TM2AM

[jkmyoung]

It's multi-level Muenchian Grouping:
Jeni's XSLT Pages: Grouping Using the Muenchian Method

<xsl:key name="vehicle-by-make" match="make" use="@xmake"/>
<xsl:key name="vehicle-by-make-model" match="make" use="concat(@make, '_', [EMAIL="model/@xmodel"]model/@xmodel[/EMAIL])"/>
...
...
<xsl:for-each select="make[count(.|key('vehicle-by-make', @xmake)[1]) = 1]">
<xsl:copy>
....
<xsl:for-each select="key('vehicle-by-make', @xmake)[count(.|key('vehicle-by-make-model', concat(@make, '_', [EMAIL="model/@xmodel)"]model/@xmodel)[/EMAIL][1]) = 1]">
...
<xsl:for-each select=key('vehicle-by-make-model', concat(@make, '_', [EMAIL="model/@xmodel)[1"]model/@xmodel)[/EMAIL]">

It's the 2nd for-each which is the most confusing.