How to select a specified item using XSLT at its index?

Question

I have an xml file here:

<DM_Function Function="attribute value">
  <DM>
    <DM_Source SourceID="id1" SourceTitle="Title1" SourceContent="content1">
    </DM_Source>
  </DM>
  <DM>
    <DM_Source SourceID="id2" SourceTitle="Title2" SourceContent="content2">
    </DM_Source>
  </DM>
  <DM>
    <DM_Source SourceID="id3" SourceTitle="Title3" SourceContent="content3">
    </DM_Source>
  </DM>
</DM_Function>

There is a variable in the XSLT file:

<xsl:param name="dmIndex" select="2" />

I want to convert an XML file to another. The variable is the index of the element, I hope another XML file just shows the Root element and the specified element (including attributes).

Answer 1

This conversion is :

<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:param name="dmIndex" select="2" />   

 <xsl:template match="/*">
    <xsl:copy>
      <xsl:copy-of select="@*"/>
      <xsl:copy-of select="DM[$dmIndex]"/>
    </xsl:copy>
 </xsl:template>
</xsl:stylesheet>

when applied to the provided XML document :

<DM_Function Function="attribute value">
  <DM>
    <DM_Source SourceID="id1" SourceTitle="Title1" SourceContent="content1">
    </DM_Source>
  </DM>
  <DM>
    <DM_Source SourceID="id2" SourceTitle="Title2" SourceContent="content2">
    </DM_Source>
  </DM>
  <DM>
    <DM_Source SourceID="id3" SourceTitle="Title3" SourceContent="content3">
    </DM_Source>
  </DM>
</DM_Function>

creates the desired, correct result :

<DM_Function Function="attribute value">
   <DM>
      <DM_Source SourceID="id2" SourceTitle="Title2" SourceContent="content2"/>
   </DM>
</DM_Function>