merge xml elements in one element using xslt-3 - xslt-3.0

Question

<?xml version="1.0" encoding="UTF-8" ?>
<mr:collection
xmlns:mr="http://www.lc.gov/mr2/slim"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.lc.gov/mr2/slim http://www.lc.gov/standards/mrxml/schema/mr21slim.xsd">
<mr:rc>
<mr:dtf tg="2000" i1="1" i2=" ">
<mr:sbf cd="a">Christoph Kolumbus</mr:sbf>
<mr:sbf cd="d">John Diter</mr:sbf>
<mr:sbf cd="b">Julie Nat</mr:sbf>
<mr:sbf cd="f">Darius Milhaud</mr:sbf>
<mr:sbf cd="g">Erich kleiber</mr:sbf>
<mr:sbf cd="g">Franz Ludwig Horth</mr:sbf>
</mr:dtf>
<mr:dtf tg="3000" i1="1" i2=" ">
<mr:sbf cd="a">Christoph Kolumbus</mr:sbf>
<mr:sbf cd="d">Serg</mr:sbf>
<mr:sbf cd="b">Mak</mr:sbf>
<mr:sbf cd="f">DarMil</mr:sbf>
<mr:sbf cd="g">Erikl</mr:sbf>
<mr:sbf cd="g">LudHorth</mr:sbf>
</mr:dtf>
</mr:rc>
<mr:rc>
<mr:dtf tg="2000" i1="1" i2="0">
<mr:sbf cd="a">Chris Prante</mr:sbf>
<mr:sbf cd="e">"Chris Dietz"</mr:sbf>
</mr:dtf>
</mr:rc>
</mr:collection>
i need to create a new xml file, by merging the elements that have the value <mr:dtf tg="2000" (irrelevant of what follows in i1 and i2 values),and of course there are other elements in the input xmlfiles with different values,ie <mr:dtf tg="3000" in the following way: the new value of the new single element that will be created will consist of the value of cd a, then a space character and the value of cd b, then a space character, the : character,again a space character, then the value of cd e, then a space character, the / character,again a space character, then the value of cd f, then a space character, the ; character,again a space character, then the value of cd g,only if the above cd elements exist.
Desired output:
<O-PM xsi:schemaLocation="http://www.op.org/O/2.0/ http://www.op.org/O/2.0/O-PM.xsd">
<ListRcs>
<rc>
<mtdt>
<e:rc>
<d:title xml:lang="el">Christoph Kolumbus Julie Nat / Darius Milhaud ; Erich kleiber ; Franz Ludwig Horth</d:title>
</e:rc>
</mtdt>
</rc>
<rc>
<mtdt>
<e:rc>
<d:title xml:lang="el">Chris Prante : "Chris Dietz"</d:title>
</e:rc>
</mtdt>
</rc>
</ListRcs>
I have tried only with xsl:value-of select, getting not the result i need... is there a more clever - efficient way to do this? Thank you

Answer 1

It is kind of hard to cater for all options of missing or existing items, perhaps the following helps as it outputs certain separators only if the item itself exists; nevertheless I haven't got the exact output, hopefully you can adjust the code to your needs:
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xpath-default-namespace="http://www.lc.gov/mr2/slim"
exclude-result-prefixes="#all"
expand-text="yes"
version="3.0">
<xsl:mode on-no-match="shallow-copy"/>
<xsl:output method="xml" indent="yes"/>
<xsl:template match="collection">
<O-PM>
<ListRcs>
<xsl:apply-templates/>
</ListRcs>
</O-PM>
</xsl:template>
<xsl:template match="rc">
<rc>
<xsl:apply-templates/>
</rc>
</xsl:template>
<xsl:template match="dtf[#tg = 2000]">
<mdtd>
<rc>
<title xml:lang="el">{sbf[#cd = 'a']} {sbf[#cd = 'b']}{sbf[#cd = 'e']!(':', .)} {sbf[#cd = 'f']!('/', .)}{(sbf[#cd = 'g'] => string-join(' ; '))!('', .)}</title>
</rc>
</mdtd>
</xsl:template>
<xsl:template match="dtf[#tg != 2000]"/>
</xsl:stylesheet>
Namespaces for the output were not declared so I have put everything in no namespace.
Example at https://xsltfiddle.liberty-development.net/pNEj9dR.