in this example I have an order with different typed items. The type is a
QName in an attribute. There are namespaces declared, having the same
prefix as the 'prefix' in the xsi:type attribute. As you can see there are
more namespaces declared as needed (whatever the reason for that case
might be). Now I would like to clean up and just keep the ones that are
'used' in the xsi:type content. The stylesheet actually already does what
I want, but I would like to know whether there might be a better way to do
it, since it looks a little hackish to me.

  <!--identity tranformation; do not copy namespaces; create namespace of
xsi:type-->
  <xsl:template match="*[@xsi:type]">
    <xsl:variable name="var.prefix"
select="substring-before(@xsi:type,':')"/>
    <xsl:copy copy-namespaces="no">
      <xsl:copy-of select="@*"/>
      <xsl:copy-of select=
            "namespace::*[name(.)=substring-before(current()/@xsi:type,':')]"/>
      <xsl:apply-templates/>
    </xsl:copy>
  </xsl:template>

~/t/ftemp $ cat heiko.xml
<?xml version="1.0" encoding="UTF-8"?>
<c:order xmlns:c="http://prods.com/c"
         xmlns:v="http://prods.com/v"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

  <v:item xsi:type="ns1:basicItem"
          xmlns:ns1="http://prods.com/ns1"
          xmlns:ns2="http://prods.com/ns2"
          xmlns:ns3="http://prods.com/ns3">
    <v:name>Basic</v:name>
    <v:number>A200338</v:number>
    <v:color>blue</v:color>
  </v:item>

  <v:item xsi:type="ns2:advancedItem"
          xmlns:ns1="http://prods.com/ns1"
          xmlns:ns2="http://prods.com/ns2"
          xmlns:ns3="http://prods.com/ns3">
    <v:name>Advanced</v:name>
    <v:number>A200339</v:number>
    <v:color>white</v:color>
    <v:pattern>stripes</v:pattern>
  </v:item>

  <v:item xsi:type="ns4:lostItem"
          xmlns:ns1="http://prods.com/ns1"
          xmlns:ns2="http://prods.com/ns2"
          xmlns:ns3="http://prods.com/ns3">
    <v:name>Lost</v:name>
    <v:number>A200340</v:number>
  </v:item>

  <v:item xmlns:ns1="http://prods.com/ns1" xsi:type="ns1:basicItem">
    <v:name>Basic</v:name>
    <v:number>A200338</v:number>
    <v:color>blue</v:color>
  </v:item>

  <v:item xmlns:ns2="http://prods.com/ns2" xsi:type="ns2:advancedItem">
    <v:name>Advanced</v:name>
    <v:number>A200339</v:number>
    <v:color>white</v:color>
    <v:pattern>stripes</v:pattern>
  </v:item>

  <v:item xsi:type="ns4:lostItem">
    <v:name>Lost</v:name>
    <v:number>A200340</v:number>
  </v:item>

</c:order>~/t/ftemp $ cat heiko.xsl
<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
version="2.0">
  <xsl:output method="xml" encoding="UTF-8"/>

  <!--identity transformation; copy namespaces-->
  <xsl:template match="*">
    <xsl:copy copy-namespaces="yes">
      <xsl:copy-of select="@*"/>
      <xsl:apply-templates/>
    </xsl:copy>
  </xsl:template>

  <!--identity tranformation; do not copy namespaces; create namespace of
xsi:type-->
  <xsl:template match="*[@xsi:type]">
    <xsl:variable name="var.prefix"
select="substring-before(@xsi:type,':')"/>
    <xsl:copy copy-namespaces="no">
      <xsl:copy-of select="@*"/>
      <xsl:copy-of select=
            "namespace::*[name(.)=substring-before(current()/@xsi:type,':')]"/>
      <xsl:apply-templates/>
    </xsl:copy>
  </xsl:template>

  <!--identity transformation; do not copy namespaces-->
  <xsl:template match="*[@xsi:type]//*">
    <xsl:copy copy-namespaces="no">
      <xsl:copy-of select="@*"/>
      <xsl:apply-templates/>
    </xsl:copy>
  </xsl:template>
</xsl:stylesheet>~/t/ftemp $

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