Question

I have a table schema which has some meta field data which I need to pull down to the row level.

So this …

<tables>
    <table name="T01">
        <columns>
            <column name="F01">
                <heading>Field 1</heading>
            </column >
            <column name="F02">
                <heading>Field 2</heading>
            </column>
        </columns>
        <rows>
            <row>
                <field name="F01">AAAAA</field>
                <field name="F02">BBBBB</field>
            </row>
            <row>
                <field name="F01">DDDDD</field>
                <field name="F02">EEEEE</field>
            </row>
        </rows>
    </table>
    <table name="T02">
        <!-- ... -->
    </table>
</tables>

should become this …

<tables>
    <table name="T01">
        <rows>
            <row>
                <field name="F01">
                    <heading>Field 1</heading>
                    <value>AAAAA</value>
                </field>
                <field name="F02">                    
                    <heading>Field 2</heading>  
                    <value>BBBBB</value>
                </field>
            </row>
            <row>
                <field name="F01">
                    <heading>Field 1</heading>
                    <value>DDDDD</value>
                </field>
                <field name="F02">                    
                    <heading>Field 2</heading>  
                    <value>EEEEE</value>
                </field>
            </row>
        </rows>
    </table>
    <table name="T02">
        <!-- ... -->
    </table>
</tables>

I am sure there are tons of simple ways to do this with XSLT, but due to my tool, I really need to retrieve the column heading via a key(). So something like this …

<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:output method="xml" indent="yes"/>

  <!-- This won't work but if it did ... -->
  <xsl:key name="field-heading"
          match="../../columns/column/heading"
          use="../@name" />

  <xsl:template match="@* | node()">
    <xsl:copy>
      <xsl:apply-templates select="@* | node()"/>
    </xsl:copy>
  </xsl:template>


  <xsl:template match="field">
    <field name="{@name}">
      <heading>
        <xsl:value-of select="key('field-heading', @name)"/>
      </heading>
      <value>
        <xsl:value-of select="."/>
      </value>
    </field>
  </xsl:template>

  <xsl:template match="columns"/>

</xsl:stylesheet>

But the xsl:key match attribute doesn’t allow the parent axis and I am not sure if there are any other ways make it fit.

Answer 1

A slightly simpler solution:

<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:key name="kColByNames" match="column" use=
  "concat(../../@name, '+', @name)"/>

 <xsl:template match="node()|@*">
     <xsl:copy>
       <xsl:apply-templates select="node()|@*"/>
     </xsl:copy>
 </xsl:template>

 <xsl:template match="field">
  <xsl:copy>
   <xsl:copy-of select="@*"/>
   <heading>
     <xsl:value-of select=
      "key('kColByNames', concat(ancestor::table[1]/@name, '+', @name))"/>
   </heading>
   <value><xsl:value-of select="."/></value>
  </xsl:copy>
 </xsl:template>
 <xsl:template match="columns"/>
</xsl:stylesheet>

When this transformation is applied on the provided XML document:

<tables>
    <table name="T01">
        <columns>
            <column name="F01">
                <heading>Field 1</heading>
            </column>
            <column name="F02">
                <heading>Field 2</heading>
            </column>
        </columns>
        <rows>
            <row>
                <field name="F01">AAAAA</field>
                <field name="F02">BBBBB</field>
            </row>
            <row>
                <field name="F01">DDDDD</field>
                <field name="F02">EEEEE</field>
            </row>
        </rows>
    </table>
    <table name="T02">
        <!-- ... -->
    </table>
</tables>

the wanted, correct result is produced:

<tables>
   <table name="T01">
      <rows>
         <row>
            <field name="F01">
               <heading>Field 1</heading>
               <value>AAAAA</value>
            </field>
            <field name="F02">
               <heading>Field 2</heading>
               <value>BBBBB</value>
            </field>
         </row>
         <row>
            <field name="F01">
               <heading>Field 1</heading>
               <value>DDDDD</value>
            </field>
            <field name="F02">
               <heading>Field 2</heading>
               <value>EEEEE</value>
            </field>
         </row>
      </rows>
   </table>
   <table name="T02"><!-- ... --></table>
</tables>

Explanation: Overriding the identity rule and using a composite key — a column is identified by the pair of its name attribute and the name attribute of its grandparent table.