xslt 1.0, select group of nodes with key - xslt

Question

I want to select nodes based on some variables.
The XML code:
<data>
<prot seq="AAA">
<node num="1">1345</node>
<node num="1">11245</node>
<node num="2">88885</node>
</prot>
<prot seq="BBB">
<node num="1">678</node>
<node num="1">456</node>
<node num="2">6666</node>
</prot>
<prot seq="CCC">
<node num="1">111</node>
<node num="1">222</node>
<node num="2">333</node>
</prot>
</data>
The XML that I want
<output>
<prot seq="AAA">
<node num="1">1345</node>
<node num="2">88885</node>
</prot>
<prot seq="BBB">
<node num="1">678</node>
<node num="2">6666</node>
</prot>
<prot seq="CCC">
<node num="1">111</node>
<node num="2">333</node>
</prot>
</data>
So, my idea has been to group the nodes with a xsl:key element, and then do a for-each of them. For example:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="xml" indent="yes" omit-xml-declaration="yes"/>
<xsl:key name="by" match="/data/prot" use="concat(#seq,'|',node/#num)"/>
<xsl:template match="/">
<root>
<xsl:apply-templates select="/data/prot"/>
</root>
</xsl:template>
<xsl:template match="/data/prot">
<xsl:for-each select="./node">
<xsl:for-each select="key('by',concat(current()/../#seq,'|',current()/#num))">
node <xsl:value-of select="./node" />
</xsl:for-each>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
but the output is not what I expected, and I cannot see what I am doing wrong. I would prefer to keep the for-each structure. It is just as if I was not using properly the xsl:key grouping features.
the output that I get, unwanted
<root>
node 1345
node 1345
node 678
node 678
node 111
node 111</root>
And the code as it to be tested
http://www.xsltcake.com/slices/sgWUFu/20
Thanks!

Answer 1

The main problem in your code is that the key indexes prot elements, but what we want to de-duplicate (and need to index) is the node elements.
Here is a short and correct solution:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:key name="nodeByParentAndNum" match="node"
use="concat(generate-id(..), '+', #num)"/>
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<xsl:template match="/*">
<data>
<xsl:apply-templates/>
</data>
</xsl:template>
<xsl:template match=
"node
[not(generate-id()
=
generate-id(key('nodeByParentAndNum',
concat(generate-id(..), '+', #num)
)
[1]
)
)
]
"/>
</xsl:stylesheet>
when this transformation is applied on the provided XML document:
<data>
<prot seq="AAA">
<node num="1">1345</node>
<node num="1">11245</node>
<node num="2">88885</node>
</prot>
<prot seq="BBB">
<node num="1">678</node>
<node num="1">456</node>
<node num="2">6666</node>
</prot>
<prot seq="CCC">
<node num="1">111</node>
<node num="1">222</node>
<node num="2">333</node>
</prot>
</data>
the wanted, correct result is produced:
<data>
<prot seq="AAA">
<node num="1">1345</node>
<node num="2">88885</node>
</prot>
<prot seq="BBB">
<node num="1">678</node>
<node num="2">6666</node>
</prot>
<prot seq="CCC">
<node num="1">111</node>
<node num="2">333</node>
</prot>
</data>