Question

I am writing an XPath expression to count unique child attribues. Using the following xPath expression I could fetch all the child attributes along with which are not unique:

//*[count(*)=0] 

I need an XPath expression to return me all the unique attributes and the count of number of unique attributes

Eg: XML file

<details>
    <Employee>
        <EmpNo>10</EmpNo>
        <EmpName>TestName</EmpName>
        <Address>
           <Address1>market</Address1>
           <Address2>motel</Address2>
           <Street/>
        </Address>
    </Employee>

    <Employee>
        <EmpNo>20</EmpNo>
        <EmpName>TestName2</EmpName>
        <Address>
           <Address1>school</Address1>
           <Address2>playground</Address2>
           <Street>
                <StreetName>TestStreet2</StreetName>
                <StreetCode>200</StreetCode>
           </Street>
        </Address>
    </Employee>

Expected output:

  <!-- Unique element's count -->
  <data>6</data>
  <!-- Unique Element Names -->
  <data>EmpNo</data>
  <data>EmpName</data>
  <data>Address1</data>
  <data>Address2</data>
  <data>StreetName</data>
  <data>StreetCode</data>
  <!-- Unique Element values -->
  <!-- Data Set 1 -->
  <data>10</data>
  <data>TestName</data>
  <data>market</data>
  <data>motel</data>
  <data>null</data>
  <data>null</data>
  <!-- Data Set 2 -->
  <data>20</data>
  <data>TestName2</data>
  <data>school</data>
  <data>playground</data>
  <data>TestStreet2</data>
  <data>200</data>

Thanks.

Answer 1

This XSLT 1.0 stylesheet

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
  <xsl:output indent="yes" omit-xml-declaration="yes" />

  <!-- index data fields by their element name -->
  <xsl:key 
    name  = "kFields" 
    match = "Employee//*"
    use   = "name()" 
  />

  <!-- store a unique list of elements (Muenchian Grouping) -->    
  <xsl:variable name="fields" select="
    /details/Employee//*[
      generate-id()
      =
      generate-id(key('kFields', name())[1])
    ][
      not(
        key('kFields', name())/*
      )
    ]
  " />

  <!-- main output ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
  <xsl:template match="/details">
    <xsl:comment> unique element count </xsl:comment>
    <data>
      <xsl:value-of select="count($fields)" />
    </data>
    <xsl:call-template name="newline" />

    <xsl:comment> unique element names </xsl:comment>
    <xsl:for-each select="$fields">
      <data>
        <xsl:value-of select="name()" />
      </data>
      <xsl:call-template name="newline" />
    </xsl:for-each>

    <xsl:comment> unique element values </xsl:comment>
    <xsl:apply-templates select="Employee" />
  </xsl:template>

  <!-- Employee output ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
  <xsl:template match="Employee">
    <xsl:variable name="this" select="." />

    <xsl:comment> data set <xsl:value-of select="position()" /> </xsl:comment>
    <xsl:for-each select="$fields">
      <xsl:variable 
        name="val" 
        select="$this//*[not(*) and name() = name(current())]" 
      />
      <data>
        <xsl:choose>
          <xsl:when test="normalize-space($val) != ''">
            <xsl:value-of select="$val" />
          </xsl:when>
          <xsl:otherwise>
            <xsl:text>null</xsl:text>
          </xsl:otherwise>
        </xsl:choose>
      </data>
      <xsl:call-template name="newline" />
    </xsl:for-each>
  </xsl:template>

  <!-- Helpers ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -->
  <xsl:template name="newline">
    <xsl:value-of select="'&#xA;'" />
  </xsl:template>

</xsl:stylesheet>

produces (line-breaks may reproduce differently for you):

<!-- unique element count -->
<data>6</data>

<!-- unique element names -->
<data>EmpNo</data>
<data>EmpName</data>
<data>Address1</data>
<data>Address2</data>
<data>StreetName</data>
<data>StreetCode</data>

<!-- unique element values -->

<!-- data set 1 -->
<data>10</data>
<data>TestName</data>
<data>market</data>
<data>motel</data>
<data>null</data>
<data>null</data>

<!-- data set 2 -->
<data>20</data>
<data>TestName2</data>
<data>school</data>
<data>playground</data>
<data>TestStreet2</data>
<data>200</data>

Notes:

• //*[count(*)=0] and //*[not(*)] are equal. The latter is nicer.
• I’ve used an <xsl:key> and Muenchian Grouping to figure out the unique element names among the descendants of <Employee>
• The XPath expression in the variable $fields, does two things:
  • First it uses Muenchian grouping of the elements to make them unique by name().
  • Then it checks the remaining elements. No element of the same name may have any children anywhere in the input (not( key('kFields', name())/* ). Otherwise <data>Street</data> would show up in the output.
• Your output format is ambiguous. If there are elements that have equal names but different nesting positions, things will get messed up.