XSLT 1.0: Muenchian grouping does not work - xslt

Question

I have the following simplified XML structure:
<?xml version="1.0" encoding="utf-8"?>
<list>
<INVOIC>
<M_INVOIC>
<G_SG25>
<S_LIN>
<id>LIN</id>
<D_1082>1</D_1082>
<C_C212>
<D_7140>7610400271943</D_7140>
<D_7143_3>EN</D_7143_3>
</C_C212>
</S_LIN>
</G_SG25>
<G_SG25>
<S_LIN>
<id>LIN</id>
<D_1082>2</D_1082>
<C_C212>
<D_7140>1234567890123</D_7140>
<D_7143_3>EN</D_7143_3>
</C_C212>
</S_LIN>
</G_SG25>
</M_INVOIC>
</INVOIC>
<INVOIC>
<SALESORDER>
<ET_VBAP>
<item>
<VBELN>0010002695</VBELN>
<POSNR>000010</POSNR>
<MATNR>000000000000400487</MATNR>
<EAN11>1234567890123</EAN11>
</item>
<item>
<VBELN>0010002695</VBELN>
<POSNR>000020</POSNR>
<MATNR>000000000000002054</MATNR>
<EAN11>5012454920549</EAN11>
</item>
<item>
<VBELN>0010002695</VBELN>
<POSNR>000030</POSNR>
<MATNR>000000000000392104</MATNR>
<EAN11>3046920921046</EAN11>
</item>
<item>
<VBELN>0010002695</VBELN>
<POSNR>000040</POSNR>
<MATNR>000000000000859146</MATNR>
<EAN11>8003340591469</EAN11>
</item>
<item>
<VBELN>0010002695</VBELN>
<POSNR>000050</POSNR>
<MATNR>000000000000727194</MATNR>
<EAN11>7610400271943</EAN11>
</item>
</ET_VBAP>
</SALESORDER>
</INVOIC>
</list>
my XSLT:
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
version="1.0">
<xsl:output method="xml" encoding="UTF-8" indent="yes"/>
<xsl:key name="kByEanPos" match="G_SG25" use="S_LIN/C_C212/D_7140"/>
<xsl:template match="/">
<xsl:variable name="uniqueSet" select="G_SG25[generate-id()=generate-id(key('kByEanPos',S_LIN/C_C212/D_7140))]"/>
<list>
<xsl:for-each select="list/INVOIC/M_INVOIC/G_SG25[generate-id()=
generate-id(key('kByEanPos',S_LIN/C_C212/D_7140))]">
<ean>
<xsl:value-of select="parent::M_INVOIC/parent::INVOIC/parent::list/INVOIC/SALESORDER/ET_VBAP/item/MATNR"/>
</ean>
</xsl:for-each>
</list>
</xsl:template>
</xsl:stylesheet>
gives me this XML output:
<?xml version="1.0" encoding="UTF-8"?>
<list>
<ean>000000000000400487</ean>
<ean>000000000000400487</ean>
</list>
But my expected XML output is:
<?xml version="1.0" encoding="UTF-8"?>
<list>
<ean>000000000000727194</ean>
<ean>000000000000400487</ean>
</list>
I am not sure of what I am doing wrong, I can't find my mistake. I think it has to do with the key that I defined.
Basically I need a key on <D_7140> and then look for that number in the structure below in EAN11 and output the MATNR right before.

Answer 1

In this line:
<xsl:value-of
select="parent::M_INVOIC/parent::INVOIC/parent::list/INVOIC/SALESORDER/ET_VBAP/item/MATNR"/>
You're climbing all the way up the node tree and back down to MATNR, so the only thing this is ever going to find is the first MATNR in the document. To locate the MATNR that corresponds to the current D_7140 in your for-each, this should work:
<xsl:value-of
select="/list/INVOIC/SALESORDER/ET_VBAP/item[EAN11 = current()/S_LIN/C_C212/D_7140]/MATNR"/>

Answer 2

If you are trying to look up item elements based on their EAN11 value, it might be worth considering using a key to do this too
<xsl:key name="item" match="item" use="EAN11" />
That way, you can reduce your xsl:value-of to just this
<xsl:value-of select="key('item', S_LIN/C_C212/D_7140)/MATNR"/>