I was trying to convert this xml file into a new one
in XSLT 2.0, but failed. The main issue is I have to
deal with one group-by with two level of elements: tab
and sub. I could not find any way to work around with
it. Help if you can.

T:\ftemp>type chun.xml
<?xml version="1.0" encoding="UTF-8"?>
<perm_testing>
   <user name="SFO">
      <tab name="YourSource">
         <sub name="Client">
            <checkpoint name="View" value="no"/>
         </sub>
      </tab>
      <tab name="Requisition">
         <sub name="General Info">
            <checkpoint name="View" value="yes"/>
         </sub>
      </tab>
      <tab name="Requisition">
         <sub name="General Info">
            <checkpoint name="Create" value="no"/>
         </sub>
      </tab>
      <tab name="Requisition">
         <sub name="General Info">
            <checkpoint name="Edit" value="no"/>
         </sub>
      </tab>
      <tab name="Requisition">
         <sub name="Discussion">
            <checkpoint name="View" value="no"/>
         </sub>
      </tab>
      <tab name="Requisition">
         <sub name="Discussion">
            <checkpoint name="Create" value="yes"/>
         </sub>
      </tab>
      <tab name="Requisition">
         <sub name="Discussion">
            <checkpoint name="Edit" value="no"/>
         </sub>
      </tab>
      <tab name="Requisition">
         <sub name="Resume/Quote">
            <checkpoint name="View" value="no"/>
         </sub>
      </tab>
   </user>
   <user name="ABC">
      <tab name="YourSource">
         <sub name="Client">
            <checkpoint name="View" value="yes"/>
         </sub>
      </tab>
      <tab name="Requisition">
         <sub name="General Info">
            <checkpoint name="View" value="yes"/>
         </sub>
      </tab>
      <tab name="Requisition">
         <sub name="General Info">
            <checkpoint name="Create" value="no"/>
         </sub>
      </tab>
   </user>
</perm_testing>

T:\ftemp>type chun.xsl
<?xml version="1.0" encoding="US-ASCII"?>
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                version="2.0">

<xsl:output indent="yes"/>
<xsl:strip-space elements="*"/>

<xsl:template match="user">
  <xsl:copy>
    <xsl:copy-of select="@*"/>
    <xsl:for-each-group select="tab" group-by="@name">
      <tab name="{@name}">
        <xsl:for-each-group select="current-group()/sub" group-by="@name">
          <sub name="{@name}">
            <xsl:apply-templates select="current-group()/checkpoint"/>
          </sub>
        </xsl:for-each-group>
      </tab>
    </xsl:for-each-group>
  </xsl:copy>
</xsl:template>

<xsl:template match="@*|node()"><!--identity for all other nodes-->
  <xsl:copy>
    <xsl:apply-templates select="@*|node()"/>
  </xsl:copy>
</xsl:template>

</xsl:stylesheet>
T:\ftemp>call xslt2 chun.xml chun.xsl chun.out

T:\ftemp>type chun.out
<?xml version="1.0" encoding="UTF-8"?>
<perm_testing>
   <user name="SFO">
      <tab name="YourSource">
         <sub name="Client">
            <checkpoint name="View" value="no"/>
         </sub>
      </tab>
      <tab name="Requisition">
         <sub name="General Info">
            <checkpoint name="View" value="yes"/>
            <checkpoint name="Create" value="no"/>
            <checkpoint name="Edit" value="no"/>
         </sub>
         <sub name="Discussion">
            <checkpoint name="View" value="no"/>
            <checkpoint name="Create" value="yes"/>
            <checkpoint name="Edit" value="no"/>
         </sub>
         <sub name="Resume/Quote">
            <checkpoint name="View" value="no"/>
         </sub>
      </tab>
   </user>
   <user name="ABC">
      <tab name="YourSource">
         <sub name="Client">
            <checkpoint name="View" value="yes"/>
         </sub>
      </tab>
      <tab name="Requisition">
         <sub name="General Info">
            <checkpoint name="View" value="yes"/>
            <checkpoint name="Create" value="no"/>
         </sub>
      </tab>
   </user>
</perm_testing>
T:\ftemp>rem Done!

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