Biztalk Map: Accumulation of unique detail elements in the header

Question

Below are the source and target schemas. I was wondering how I can achieve a mapping where the element "country" in the detail are promoted to the header where the list contains only unique country names with quantity defaulted to 1. In the example
below, from each of the subcategories, the countries are picked up and only unique ones appear in the output's header.
<Category CatId=1 CatName=Bikes Function=Travel>
<SubCat SubCatId=1 SubCatName=Avon>
<Countries>
<Country Name="Canada" Quantity=20 />
<Country Name="USA" Quantity=22 />
<Country Name="NZ" Quantity=30 />
</Countries>
</SubCat>
<SubCat SubCatId=2 SubCatName=Hero>
<Countries>
<Country Name="Canada" Quantity=20 />
<Country Name="Mexico" Quantity=5 />
<Countries>
</SubCat>
<SubCat SubCatId=3 SubCatName=Jet>
<Countries>
<Country Name="UK" Quantity=15 />
<Country Name="USA" Quantity=5 />
<Country Name="Germany" Quantity=2 />
<Countries>
</SubCat>
</Category>
<Category CatId=1 CatName=Bikes Function=Travel>
<Countries>
<Country Name="Canada" Quantity=1 />
<Country Name="USA" Quantity=1 />
<Country Name="NZ" Quantity=1 />
<Country Name="Mexico" Quantity=1 />
<Country Name="UK" Quantity=1 />
<Country Name="Germany" Quantity=1 />
</Countries>
<SubCat SubCatId=1 SubCatName=Avon>
<Countries>
<Country Name="Canada" Quantity=20 />
<Country Name="USA" Quantity=22 />
<Country Name="NZ" Quantity=30 />
</Countries>
</SubCat>
<SubCat SubCatId=2 SubCatName=Hero>
<Countries>
<Country Name="Canada" Quantity=20 />
<Country Name="Mexico" Quantity=5 />
<Countries>
</SubCat>
<SubCat SubCatId=3 SubCatName=Jet>
<Countries>
<Country Name="UK" Quantity=15 />
<Country Name="USA" Quantity=5 />
<Country Name="Germany" Quantity=2 />
<Countries>
</SubCat>
</Category>

Answer 1

ZIntegrator,
You can try following custom xslt
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:msxsl="urn:schemas-microsoft-com:xslt"
exclude-result-prefixes="msxsl">
<xsl:output method="xml" indent="yes" omit-xml-declaration="yes"/>
<xsl:key name="country" match="//Country/@Name" use="." />
<xsl:template match="/">
<xsl:element name="Category">
<xsl:copy-of select="//Category/@*" />
<xsl:apply-templates select="Category" />
<xsl:apply-templates select="//SubCat" mode="CopyRest" />
</xsl:element>
</xsl:template>
<xsl:template match="Category">
<xsl:for-each select="SubCat/Countries/Country/@Name[generate-id()= generate-id(key('country',.)[1])]">
<xsl:element name="Country">
<xsl:value-of select="."/>
</xsl:element>
</xsl:for-each>
</xsl:template>
<xsl:template match="@* | node()" mode="CopyRest">
<xsl:copy>
<xsl:apply-templates select="@* | node()" mode="CopyRest"/>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>
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