Recursive transformation with XSLT: Table to tree

Question

I want to transfor hierarchical elements that represent a tree. The data is provided inside a table in this format:

<?xml version="1.0" encoding="utf-16"?>
<asx:abap xmlns:asx="http://www.sap.com/abapxml" version="1.0">
    <asx:values>
        <CONCEPTS>
            <item>
                <NO>1</NO>
                <NS_PREFIX>de-gaap-ci</NS_PREFIX>
                <XBRL_ID>bs.ass.monetary</XBRL_ID>
                <IS_TUPLE>false</IS_TUPLE>
                <FATHER_ID/>
                <CONTEXT_REF>D-2012</CONTEXT_REF>
                <UNIT_REF>EUR</UNIT_REF>
                <DECIMALS>2</DECIMALS>
                <PRECISION/>
                <IS_NIL>false</IS_NIL>
                <VALUE>12923.00-</VALUE>
            </item>
            <item>
                <NO>2</NO>
                <NS_PREFIX>de-gaap-ci</NS_PREFIX>
                <XBRL_ID>bs.ass.string</XBRL_ID>
                <IS_TUPLE>false</IS_TUPLE>
                <FATHER_ID/>
                <CONTEXT_REF>D-2012</CONTEXT_REF>
                <UNIT_REF/>
                <DECIMALS/>
                <PRECISION/>
                <IS_NIL>false</IS_NIL>
                <VALUE>Test String</VALUE>
            </item>
            <item>
                <NO>3</NO>
                <NS_PREFIX>de-gaap-ci</NS_PREFIX>
                <XBRL_ID>bs.ass.nil</XBRL_ID>
                <IS_TUPLE>false</IS_TUPLE>
                <FATHER_ID/>
                <CONTEXT_REF>D-2012</CONTEXT_REF>
                <UNIT_REF/>
                <DECIMALS/>
                <PRECISION/>
                <IS_NIL>true</IS_NIL>
                <VALUE/>
            </item>
            <item>
                <NO>4</NO>
                <NS_PREFIX>de-gaap-ci</NS_PREFIX>
                <XBRL_ID>bs.ass.tuple1</XBRL_ID>
                <IS_TUPLE>true</IS_TUPLE>
                <FATHER_ID/>
                <CONTEXT_REF>D-2012</CONTEXT_REF>
                <UNIT_REF/>
                <DECIMALS/>
                <PRECISION/>
                <IS_NIL>false</IS_NIL>
                <VALUE/>
            </item>
            <item>
                <NO>5</NO>
                <NS_PREFIX>de-gaap-ci</NS_PREFIX>
                <XBRL_ID>bs.ass.a</XBRL_ID>
                <IS_TUPLE>false</IS_TUPLE>
                <FATHER_ID>bs.ass.tuple1</FATHER_ID>
                <CONTEXT_REF>D-2012</CONTEXT_REF>
                <UNIT_REF/>
                <DECIMALS/>
                <PRECISION/>
                <IS_NIL>false</IS_NIL>
                <VALUE>Value for bs.ass.a</VALUE>
            </item>
            <item>
                <NO>6</NO>
                <NS_PREFIX>de-gaap-ci</NS_PREFIX>
                <XBRL_ID>bs.ass.b</XBRL_ID>
                <IS_TUPLE>false</IS_TUPLE>
                <FATHER_ID>bs.ass.tuple1</FATHER_ID>
                <CONTEXT_REF>D-2012</CONTEXT_REF>
                <UNIT_REF/>
                <DECIMALS/>
                <PRECISION/>
                <IS_NIL>false</IS_NIL>
                <VALUE>Value for bs.ass.b</VALUE>
            </item>
        </CONCEPTS>
        <CONTEXTS>
            <item>
                <ID>D-2012</ID>
                <SCHEME>http://www.rzf-nrw.de/Steuernummer</SCHEME>
                <IDENTIFIER>5117050051729</IDENTIFIER>
                <IS_INSTANT>false</IS_INSTANT>
                <DATE_A>2012-08-28</DATE_A>
                <DATE_B>2012-08-30</DATE_B>
            </item>
            <item>
                <ID>I-2012</ID>
                <SCHEME>http://www.rzf-nrw.de/Steuernummer</SCHEME>
                <IDENTIFIER>5117050051729</IDENTIFIER>
                <IS_INSTANT>true</IS_INSTANT>
                <DATE_A>2012-08-28</DATE_A>
                <DATE_B/>
            </item>
        </CONTEXTS>
        <UNITS>
            <item>
                <ID>EUR</ID>
                <MEASURE_NS>iso4217</MEASURE_NS>
                <MEASURE_VALUE>EUR</MEASURE_VALUE>
            </item>
                        (...)
        </UNITS>
        <NAMESPACES>
            <item>
                <PREFIX>de-gcd</PREFIX>
                <URI>http://www.xbrl.de/taxonomies/de-gcd-2011-09-14</URI>
                <IS_DEFAULT>false</IS_DEFAULT>
            </item>
                        (...)
        </NAMESPACES>
        <SCHEMAS>
            <item>
                <SCHEMA_REF>http://www.xbrl.de/taxonomies/de-gcd-2011-09-14.xsd</SCHEMA_REF>
            </item>
                        (...)
        </SCHEMAS>
    </asx:values>
</asx:abap>

The column IS_TUPLE says that this element is a father node inside the tree. All -elements that have the XBRL_ID of this father inside the column FATHER_ID are supposed to be the children of this father. Hence, if the column FATHER_ID is empty the node has no father.

I want to process these elements recursively with XSLT. The target format is XBRL which is basically XML. Here is my attempt:

<xsl:template match="/">
<xbrl ...>
   <xsl:apply-templates select="/CONCEPTS/item">
      <xsl:with-param name="rec_father_node" select="/" />
   </xsl:apply-templates>
</xbrl>
</xsl:template>

<xsl:template name="tpl_concept" match="/CONCEPTS/item">

    <xsl:param name="rec_father_node"/>

    <xsl:variable name="rec_father_id" select="string($rec_father_node/XBRL_ID/text())"/>

    <xsl:variable name="father_id" select="string(*[local-name()='FATHER_ID'])"/>
    <xsl:variable name="is_tuple" select="string(*[local-name()='IS_TUPLE'])"/>     
    <xsl:variable name="ns_prefix" select="string(*[local-name()='NS_PREFIX'])"/>
    <xsl:variable name="xbrl_id" select="string(*[local-name()='XBRL_ID'])"/>
    <xsl:variable name="name" select="$xbrl_id"/>

    <xsl:if test="$is_tuple = 'false' and $rec_father_id = $father_id">

        <xsl:element name="{$name}">
                      (...)
        </xsl:element>
    </xsl:if>

    <xsl:if test="$is_tuple = 'true' and $rec_father_id = $father_id">
        <xsl:element name="{$name}">
            <xsl:choose>
                <xsl:when test="$is_nil = 'true'">
                    <xsl:attribute name="xsi:nil">true</xsl:attribute>
                </xsl:when>
                <xsl:otherwise>
                    <xsl:apply-templates select="/CONCEPTS/item">
                        <xsl:with-param name="rec_father_id" select="current()" />
                    </xsl:apply-templates>                  
                </xsl:otherwise>
            </xsl:choose>
        </xsl:element>
    </xsl:if>       
</xsl:template>

My idea was the following: nodes that are no father have the string value of '' inside the column FATHER_ID. Therefore, I pass the root node to the parameter rec_father_node to get this initial string. With the recursive call of the same template the parameter rec_father_node contains the node of this father so I can read out the XBRL_ID of this father to only add elements that have this value inside the column FATHER_ID.

My problem is the following: the parameter rec_father_node looses its value passed by the recursion call. The value is always the root node which is passed by the initial <xsl:apply-templates .../> call.

Is there a way to pass a parameter to recursive template calls? Or in general, how can I transform this flat table into a XML node tree with nested elements?

The target of the transformation should look like this (taken names from the example above and added some other nodes for clarity):

<?xml version="1.0" encoding="UTF-8"?>
<xbrl>
    <bs.ass.monetary>12923.00-</bs.ass.monetary>
    <bs.ass.string>Test String</bs.ass.string>
    <bs.ass.nil></bs.ass.nil>
    <bs.ass.tuple1>
        <bs.ass.a>Value for bs.ass.a</bs.ass.a>
        <bs.ass.b>Value for bs.ass.b</bs.ass.b>
    </bs.ass.tuple1>
</xbrl>

Thanks for any help or comments!

Although it is always good to keep your input sample as small as possible, it also would help more if your output sample corresponded directly with the input. Thanks! — Tim C, Aug 31 '12 at 10:31
Okay, I updated both the source I want to transform into the original one and updated the wanted output. I comment on your answer. It basically works, but I have still a problem. Thanks for your help so far! — , Aug 31 '12 at 12:05
Now it is updated. For some reason stackoverflow didn't save my changes! — , Aug 31 '12 at 12:22
I've updated my answer so you should now get the expected output. — Tim C, Aug 31 '12 at 12:54

Tim C · Accepted Answer · 2012-08-31T12:26:22.787

What you could do is firstly define a key to look up 'child' items based on their FATHER_ID elements.

<xsl:key name="children" match="item" use="FATHER_ID" />

Firstly though you would start off by matching items with no father

<xsl:apply-templates select="item[FATHER_ID='']"/>

Then, for items which are 'tuples' you could match them, and recursively match their children with a key

<xsl:template match="item[IS_TUPLE='true']">
   <xsl:element name="{XBRL_ID}">
      <xsl:apply-templates select="key('children', XBRL_ID)" />
   </xsl:element>
</xsl:template>

You would also have another template for item elements, which would match non-tuples, which would output whatever value you like.

Try the following XSLT

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
   <xsl:output method="xml" indent="yes"/>
   <xsl:key name="children" match="item" use="FATHER_ID"/>

   <xsl:template match="/">
         <xsl:apply-templates select="//CONCEPTS"/>
   </xsl:template>

   <xsl:template match="CONCEPTS">
      <xbrl>
         <xsl:apply-templates select="item[FATHER_ID='']"/>
      </xbrl>
   </xsl:template>

   <xsl:template match="item[IS_TUPLE='true']">
      <xsl:element name="{XBRL_ID}">
         <xsl:apply-templates select="key('children', XBRL_ID)"/>
      </xsl:element>
   </xsl:template>

   <xsl:template match="item">
      <xsl:element name="{XBRL_ID}">
         <xsl:value-of select="VALUE" />
      </xsl:element>
   </xsl:template>
</xsl:stylesheet>

When applied to your sample, you get the following

<xbrl>
   <bs.ass.monetary>12923.00-</bs.ass.monetary>
   <bs.ass.string>Test String</bs.ass.string>
   <bs.ass.nil></bs.ass.nil>
   <bs.ass.tuple1>
      <bs.ass.a>Value for bs.ass.a</bs.ass.a>
      <bs.ass.b>Value for bs.ass.b</bs.ass.b>
   </bs.ass.tuple1>
</xbrl>

Recursive transformation with XSLT: Table to tree

1 Answers1