XSLT - Generate easier xml structure to avoid grouping - xslt

Question

How can I convert this document:
<Root>
<!-- yes, I know I don't need a 'Root' element! Legacy code... -->
<Plans>
<Plan AreaID="1" UnitID="83">
<Part ID="9122" Name="foo" />
<Part ID="9126" Name="bar" />
</Plan>
<Plan AreaID="1" UnitID="86">
<Part ID="8650" Name="baz" />
</Plan>
<Plan AreaID="2" UnitID="26">
<Part ID="215" Name="quux" />
</Plan>
<Plan AreaID="1" UnitID="95">
<Part ID="7350" Name="meh" />
</Plan>
</Plans>
</Root>
to:
<areas>
<area id="1">
<unit id="83">
<part id="9122">foo</part>
<part id="9126">bar</part>
</unit>
<unit id="86">
<part id="8650">baz</part>
</unit>
<unit id="95">
<part id="7350">meh</part>
</unit>
</area>
<area id="2">
<unit id="26">
<part id="215">quux</part>
</unit>
</area>
</areas>
Do I need to group area elements?

Answer 1

Here is a sample stylesheet
<xsl:stylesheet
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:output indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:key name="k1" match="Plan" use="#AreaID"/>
<xsl:template match="Plans">
<areas>
<xsl:apply-templates select="Plan[generate-id() = generate-id(key('k1', #AreaID)[1])]" mode="group"/>
</areas>
</xsl:template>
<xsl:template match="Plan" mode="group">
<area id="{#AreaID}">
<xsl:apply-templates select="key('k1', #AreaID)"/>
</area>
</xsl:template>
<xsl:template match="Plan">
<unit id="{#UnitID}">
<xsl:apply-templates/>
</unit>
</xsl:template>
<xsl:template match="Part">
<part id="{#ID}">
<xsl:value-of select="#Name"/>
</part>
</xsl:template>
</xsl:stylesheet>