Recursive XLST

amit_sri24 · November 30th, 2011, 04:50 AM

Hi All,

I am trying to achieve one XSLT mapping requirement for the below source structure.The values under "Level" and "Parent" source field dynamically determine the target structure node "SPM" occurrence and its hierachy on the target side.

Code:

<?xml version="1.0" encoding="UTF-8"?>
<ns0:MT_Test xmlns:ns0="http://test">
   <Header>
      <Name>xx</Name>
      <Age>12</Age>
      <Item>
         <Level>1</Level>
         <Parent>0</Parent>
         <Company>A</Company>
      </Item>
      <Item>
         <Level>2</Level>
         <Parent>1</Parent>
         <Company>B</Company>
      </Item>
      <Item>
         <Level>3</Level>
         <Parent>2</Parent>
         <Company>C</Company>
      </Item>
      <Item>
         <Level>2</Level>
         <Parent>1</Parent>
         <Company>D</Company>
      </Item>
      <Item>
         <Level>3</Level>
         <Parent>2</Parent>
         <Company>E</Company>
      </Item>
      <Item>
         <Level>3</Level>
         <Parent>2</Parent>
         <Company>F</Company>
      </Item>
   </Header>
</ns0:MT_Test>

Target:

Code:

<?xml version="1.0" encoding="UTF-8"?>
<MT_Target xmlns:ns0="http://test">
   <Records>
      <Name>xx</Name>
      <Age>12</Age>
      <SPM>
         <Level>1</Level>
         <Parent>0</Parent>
         <Company>A</Company>
              <SPM>
            <Level>2</Level>
            <Parent>1</Parent>
            <Company>B</Company>
                   <SPM>
                   <Level>3</Level>
                   <Parent>2</Parent>
                   <Company>C</Company>
                    </SPM>
              </SPM>
              <SPM>
                  <Level>2</Level>
                  <Parent>1</Parent>
                  <Company>D</Company>
                  <SPM>
                     <Level>3</Level>
                     <Parent>2</Parent>
                     <Company>E</Company>
                  </SPM>
                  <SPM>
                    <Level>3</Level>
                     <Parent>2</Parent>
                     <Company>F</Company>
                 </SPM> 
             </SPM>
      </SPM>
   </Records>
</MT_Target>

Please help.

Thanks!!

amit_sri24 · November 30th, 2011, 10:26 AM

Any inputs will highly be appreciated??

Thanks in advance!!

Martin Honnen · November 30th, 2011, 11:45 AM

I am trying to understand your requirements. I run your target output through a pretty printer, then it looks like this:

Code:

<MT_Target xmlns:ns0="http://test">
  <Records>
    <Name>xx</Name>
    <Age>12</Age>
    <SPM>
      <Level>1</Level>
      <Parent>0</Parent>
      <Company>A</Company>
      <SPM>
        <Level>2</Level>
        <Parent>1</Parent>
        <Company>B</Company>
        <SPM>
          <Level>3</Level>
          <Parent>2</Parent>
          <Company>C</Company>
        </SPM>
      </SPM>
      <SPM>
        <Level>2</Level>
        <Parent>1</Parent>
        <Company>D</Company>
        <SPM>
          <Level>3</Level>
          <Parent>2</Parent>
          <Company>E</Company>
        </SPM>
        <SPM>
          <Level>3</Level>
          <Parent>2</Parent>
          <Company>F</Company>
        </SPM>
      </SPM>
    </SPM>
  </Records>
</MT_Target>

How is the parent -> child relationship determined? As the "Item" elements in the input XML don't have any id I am not sure how to determine to which parent "Item" a child "Item" belongs. Is that simply by sibling relation in the XML input?

And please state whether you want an XSLT 2.0 or 1.0 solution as grouping is much easier in XSLT 2.0.

mhkay · November 30th, 2011, 11:49 AM

You will find an example of a stylesheet that tackles a similar problem (converting a hierarchy expressed through level numbers into one expressed through XML nesting) here:

http://www.saxonica.com/papers/ideadb-1.1/mhk-paper.xml

Martin Honnen · November 30th, 2011, 12:38 PM

Assuming you can use XSLT 2.0 as support by Saxon 9 or AltovaXML and the parent "Item" is the nearest preceding sibling "Item" with a "Level" being one less the actual level you can use code like the following:

Code:

<xsl:stylesheet
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:xs="http://www.w3.org/2001/XMLSchema"
  xmlns:mf="http://example.com/mf"
  exclude-result-prefixes="mf xs"
  version="2.0">
  
  <xsl:param name="start-level" as="xs:integer" select="1"/>
  
  <xsl:output indent="yes"/>
  <xsl:strip-space elements="*"/>
  
  <xsl:function name="mf:group" as="element(SMP)*">
    <xsl:param name="items" as="element(Item)*"/>
    <xsl:param name="level" as="xs:integer"/>
    <xsl:for-each-group select="$items" group-starting-with="Item[Level = $level]">
      <SMP>
        <xsl:apply-templates select="*"/>
        <xsl:sequence select="mf:group(current-group() except ., $level + 1)"/>
      </SMP>
    </xsl:for-each-group>
  </xsl:function>
  
  <xsl:template match="@* | node()">
    <xsl:copy>
      <xsl:apply-templates select="@* | node()"/>
    </xsl:copy>
  </xsl:template>

  <xsl:template match="Header">
    <xsl:copy>
      <xsl:apply-templates select="Name, Age"/>
      <xsl:sequence select="mf:group(Item, $start-level)"/>
    </xsl:copy>
  </xsl:template>
  
</xsl:stylesheet>

amit_sri24 · December 1st, 2011, 02:50 AM

Hi Martin/Michael,

Thanks for ur reply.
I am using XSLT 1.0
>>How is the parent -> child relationship determined?

In the source structure the values under Level and Parent elements(under Item) will determine the hirearchy of SPM node on the target structure.

Please allow me to explain this using one example...
1) under first Item occ Level=1 and Parent=0
so the output will be :
<SPM>
<Level>1</Level>
<Parent>0</Parent>
<Company>A</Company>
</SPM>

2)If we have one more item i.e under Second Item node values under element Level=2 and Parent=1 respectively
so the output will be :

Code:

   <SPM>
         <Level>1</Level>
         <Parent>0</Parent>
         <Company>A</Company>
         <SPM>
            <Level>2</Level>
            <Parent>1</Parent>
             <Company>B</Company>
         </SPM>
      </SPM>

3) Now consider if i have third Item occurrence on the source side having Level=3 and Parent=2 as the element values
Output will be:

Code:

 <SPM>
         <Level>1</Level>
         <Parent>0</Parent>
         <Company>A</Company>
         <SPM>
            <Level>2</Level>
            <Parent>1</Parent>
            <Company>B</Company>
            <SPM>
               <Level>3</Level>
               <Parent>2</Parent>
               <Company>C</Company>
            </SPM>
         </SPM>
      </SPM>

4) (Now the catch is here) Fourth Item occurrence on the source side having Level=2 and Parent=1 (again) as the element values
Output will be:

Code:

 <SPM>
         <Level>1</Level>
         <Parent>0</Parent>
          <Company>A</Company>
         <SPM>
            <Level>2</Level>
            <Parent>1</Parent>
             <Company>B</Company>
            <SPM>
               <Level>3</Level>
               <Parent>2</Parent>
                <Company>C</Company>
            </SPM>
         </SPM>
          <SPM>
               <Level>2</Level>
               <Parent>1</Parent>
               <Company>D</Company>
            </SPM>
      </SPM>

The values in Level and Parent will always be having (n,n-1) relation....

And one more thing please let me know how to assign points??

Thanks!!

mhkay · December 1st, 2011, 05:10 AM

>I am using XSLT 1.0

Then you are a brave man (or woman). I'm afraid I don't have the time or patience to help you solve this using XSLT 1.0.

amit_sri24 · December 1st, 2011, 05:41 AM

Hi,
I can able to make a basic skelton of xslt but cant able to make the logic work when the Level and Parent starts repeating again for instance the case number 4 explained in my previous post

Code:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:ns0="http://test">
   <xsl:template match="/">
      <MT_Target>
         <Records>
            <Name>
               <xsl:value-of select="ns0:MT_Test/SPL_Header/Name"/>
            </Name>
            <Age>
               <xsl:value-of select="ns0:MT_Test/SPL_Header/Age"/>
            </Age>
            <xsl:variable name="Max_No">
               <xsl:value-of select="count(//SPL_Item)"/>
            </xsl:variable>
            <xsl:call-template name="Loop">
               <xsl:with-param name="i">1</xsl:with-param>
               <xsl:with-param name="k" select="$Max_No"/>
            </xsl:call-template>
         </Records>
      </MT_Target>
   </xsl:template>
   <xsl:template name="Loop">
      <xsl:param name="i"/>
      <xsl:param name="k"/>
      <xsl:if test="$i &lt;= $k">
         <xsl:variable name="kk">
            <xsl:value-of select="//SPL_Item[$i]/Parent"/>
         </xsl:variable>
         <xsl:variable name="kk1">
            <xsl:value-of select="//SPL_Item[$i+1]/Parent"/>
         </xsl:variable>
         <SPM>
            <Level>
               <xsl:value-of select="//SPL_Item[$i]/Level"/>
            </Level>
            <Parent>
               <xsl:value-of select="//SPL_Item[$i]/Parent"/>
            </Parent>
            <Company>
               <xsl:value-of select="//SPL_Item[$i]/Company"/>
            </Company>
            <xsl:if test="$kk1&gt;$kk">
               <xsl:call-template name="Loop">
                  <xsl:with-param name="i">
                     <xsl:value-of select="$i + 1"/>
                  </xsl:with-param>
                  <xsl:with-param name="k">
                     <xsl:value-of select="$k"/>
                  </xsl:with-param>
               </xsl:call-template>
            </xsl:if>
         </SPM>
      </xsl:if>
   </xsl:template>
</xsl:stylesheet>

samjudson · December 1st, 2011, 05:54 AM

The following seems to work:

Code:

<xsl:template match="ns0:MT_Test">
	<MT_Test>
		<xsl:apply-templates/>
	</MT_Test>
</xsl:template>

<xsl:template match="Header">
	<Records>
		<Name><xsl:value-of select="Name"/></Name>
		<Age><xsl:value-of select="Age"/></Age>
    	<xsl:call-template name="process_items">
    		<xsl:with-param name="level" select="1"/>
    		<xsl:with-param name="items" select="Item"/>
    	</xsl:call-template>
	</Records>
</xsl:template>

<xsl:template name="process_items">
  <xsl:param name="level"/>
  <xsl:param name="items"/>

  <xsl:for-each select="$items[Level=$level]">
  	<xsl:variable name="this" select="."/>
  	<SPM>
  	  <Level><xsl:value-of select="Level"/></Level>
  	  <Parent><xsl:value-of select="Parent"/></Parent>
  	  <Company><xsl:value-of select="Company"/></Company>
  	  
  	  <xsl:call-template name="process_items">
  	  	<xsl:with-param name="level" select="$level+1"/>
  	  	<xsl:with-param name="items" select="following-sibling::Item[generate-id(preceding-sibling::Item[Level=$level][1])=generate-id($this)]"/>
  	  </xsl:call-template>
  	</SPM>
  </xsl:for-each>
</xsl:template>

amit_sri24 · December 1st, 2011, 07:13 AM

Hi Sam,
That was an awesome answer...u made my day

Thanks!!