XSLT removing children from parent dynamically - xslt

Question

To avoid having to hard code the child element names I want to remove, I'd like to make a dynamic process to remove child elements when a matching parent element name is found.
My XML file:
<A>
<B1>
<C>C</C>
<D>D</D>
<E>E</E>
<H>H</H>
<MOD>
<C>C</C>
<D>D</D>
<E>E</E>
<F>F</F>
<G>G</G>
</MOD>
</B1>
<B2>
<C>C</C>
<E>E</E>
<H>H</H>
<MOD>
<C>C</C>
<D>D</D>
<E>E</E>
<F>F</F>
<G>G</G>
</MOD>
</B2>
<B3>
<D>D</D>
<E>E</E>
<H>H</H>
<X>X</X>
<MOD>
<C>C</C>
<D>D</D>
<E>E</E>
<F>F</F>
<G>G</G>
<X>G</X>
</MOD>
</B3>
</A>
Desired output:
My XML file:
<A>
<B1>
<C>C</C>
<D>D</D>
<E>E</E>
<H>H</H>
<MOD>
<F>F</F>
<G>G</G>
</MOD>
</B1>
<B2>
<C>C</C>
<E>E</E>
<H>H</H>
<MOD>
<D>D</D>
<F>F</F>
<G>G</G>
</MOD>
</B2>
<B3>
<D>D</D>
<E>E</E>
<H>H</H>
<X>X</X>
<MOD>
<C>C</C>
<F>F</F>
<G>G</G>
</MOD>
</B3>
</A>
My XSLT
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
exclude-result-prefixes="xs">
<xsl:strip-space elements="*"/>
<!-- copy all nodes -->
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<!-- Remove child elements but keep parent element with same name -->
<xsl:template match="C[../ancestor::*/C]"/>
<xsl:template match="D[../ancestor::*/D]"/>
<xsl:template match="E[../ancestor::*/E]"/>
</xsl:stylesheet>
I think I can combine the remove element code like this
<xsl:template match="C|D|E[../ancestor::*/C|D|E]"/>
I'm not sure how to start, but I'm thinking the process would have to get the parent node names (C,D,E,H), cycle through the children comparing the parent node name to each child node name. When a match is found, remove the child element. Thanks.

Answer 1

As far as I can tell, this stylesheet does what you need. It produces output matching what you say you need by excluding elements that have a parent with a preceding sibling of the same name.
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform" >
<xsl:strip-space elements="*"/>
<xsl:output method="xml" omit-xml-declaration="yes" indent="yes"/>
<xsl:template match="*">
<xsl:if test="not(parent::*/preceding-sibling::*[name() = name(current())])">
<xsl:copy>
<xsl:apply-templates/>
</xsl:copy>
</xsl:if>
</xsl:template>
</xsl:stylesheet>

Answer 2

When this XSLT:
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:template match="#*|node()">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
</xsl:copy>
</xsl:template>
<xsl:template
match="MOD/*[../../* = self::* or preceding-sibling::* = self::*]"/>
</xsl:stylesheet>
...is applied against the provided XML:
<A>
<B1>
<C>C</C>
<D>D</D>
<E>E</E>
<H>H</H>
<MOD>
<C>C</C>
<D>D</D>
<E>E</E>
<F>F</F>
<G>G</G>
</MOD>
</B1>
<B2>
<C>C</C>
<E>E</E>
<H>H</H>
<MOD>
<C>C</C>
<D>D</D>
<E>E</E>
<F>F</F>
<G>G</G>
</MOD>
</B2>
<B3>
<D>D</D>
<E>E</E>
<H>H</H>
<X>X</X>
<MOD>
<C>C</C>
<D>D</D>
<E>E</E>
<F>F</F>
<G>G</G>
<X>G</X>
</MOD>
</B3>
</A>
...the wanted result is produced:
<A>
<B1>
<C>C</C>
<D>D</D>
<E>E</E>
<H>H</H>
<MOD>
<F>F</F>
<G>G</G>
</MOD>
</B1>
<B2>
<C>C</C>
<E>E</E>
<H>H</H>
<MOD>
<D>D</D>
<F>F</F>
<G>G</G>
</MOD>
</B2>
<B3>
<D>D</D>
<E>E</E>
<H>H</H>
<X>X</X>
<MOD>
<C>C</C>
<F>F</F>
<G>G</G>
</MOD>
</B3>
</A>
Explanation:
The first template is the well-known Identity Template, which copies all nodes and attributes from the source document to the result document.
The second template overrides the first and effectively removes all children of <MOD> that:
have the same name as a previous sibling or
have the same name as a sibling of their <MOD> parent (an "uncle-or-aunt")