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Creating nested XML using the muenchian method in XLST

I am trying to create a nested XML document from a flat XML document as shown below. After searching here for other resources available on the network, it seems that the muenchain method may be the solution, however I struggle with its application to my situation.

The XML I need to translate takes the form:

<i> <item id="1" name="one" sub_id="10" sub_name="s1" detail_id="t1" detail_name="aaaa"/> <item id="1" name="one" sub_id="10" sub_name="s1" detail_id="t2" detail_name="bbb"/> <item id="1" name="one" sub_id="20" sub_name="s2" detail_id="t1" detail_name="ccc"/> <item id="1" name="one" sub_id="20" sub_name="s2" detail_id="t2" detail_name="ddd"/> <item id="2" name="two" sub_id="10" sub_name="s1" detail_id="t1" detail_name="eee"/> <item id="2" name="two" sub_id="10" sub_name="s1" detail_id="t2" detail_name="fff"/> <item id="2" name="two" sub_id="20" sub_name="s2" detail_id="t1" detail_name="ggg"/> <item id="2" name="two" sub_id="20" sub_name="s2" detail_id="t2" detail_name="hhh"/> <item id="3" name="three" /> <item id="4" name="four" sub_id="10" sub_name="s1" detail_id="t1" detail_name="mmm"/> <item id="4" name="four" sub_id="10" sub_name="s1" detail_id="t2" detail_name="nnn"/> <item id="4" name="four" sub_id="20" sub_name="s2" detail_id="t1" detail_name="ooo"/> <item id="4" name="four" sub_id="20" sub_name="s2" detail_id="t2" detail_name="ppp"/> </i>

I would like to convert this to XML in the following form:

  <i> <item id="1" name="one" sub_items="true"> <sub_item sub_id="10" sub_name="s1"> <detail detail_id="t1" detail_name="aaaa"/> <detail detail_id="t2" detail_name="bbb"/> </sub_item> <sub_item sub_id="20" sub_name="s2"> <detail detail_id="t1" detail_name="ccc"/> <detail detail_id="t2" detail_name="ddd"/> </sub_item> </item> <item id="2" name="two" sub_items="true"> <sub_item sub_id="10" sub_name="s1"> <detail detail_id="t1" detail_name="eee"/> <detail detail_id="t2" detail_name="fff"/> </sub_item> <sub_item sub_id="20" sub_name="s2"> <detail detail_id="t1" detail_name="ggg"/> <detail detail_id="t2" detail_name="hhh"/> </sub_item> </item> <item id="3" name="three" sub_items="false"/> <item id="4" name="four" sub_items="true"> <sub_item sub_id="10" sub_name="s1"> <detail detail_id="t1" detail_name="mmm"/> <detail detail_id="t2" detail_name="nnn"/> </sub_item> <sub_item sub_id="20" sub_name="s2"> <detail detail_id="t1" detail_name="ooo"/> <detail detail_id="t2" detail_name="ppp"/> </sub_item> </item> </i>

From my research, I have the following XLST to do the conversion. I use the key method for the id attribute of the element. This does not group the data, repeating everything correctly for a given element identifier at each level, which makes sense given the key. So my problem is how can I select the nodes needed to output each level of the socket, do I need to use a different key operator?

 <?xml version="1.0" encoding="utf-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:key name="indexes" match="i/item" use="@id"/> <xsl:template match="i"> <i> <xsl:for-each select="item[count(. | key('indexes',@id)[1]) = 1]" > <xsl:sort select="@id"/> <item> <xsl:attribute name="id"> <xsl:value-of select="@id"/> </xsl:attribute> <xsl:attribute name="name"> <xsl:value-of select="@name"/> </xsl:attribute> <xsl:attribute name="hasRows"> <xsl:value-of select="@id"/> </xsl:attribute> <xsl:for-each select="key('indexes',@id)"> <subitem> <xsl:attribute name ="sub_id"> <xsl:value-of select="@sub_id"/> </xsl:attribute> <xsl:attribute name ="sub_name"> <xsl:value-of select="@sub_name"/> </xsl:attribute> <xsl:for-each select="key('indexes',@id)"> <segment> <xsl:attribute name ="detail_id"> <xsl:value-of select="@detail_id"/> </xsl:attribute> <xsl:attribute name ="detail_name"> <xsl:value-of select="@detail_name"/> </xsl:attribute> </segment> </xsl:for-each> </subitem> </xsl:for-each> </item> </xsl:for-each> </i> </xsl:template> </xsl:stylesheet>

Is it also possible to populate the * sub_items * attribute with true when subitems / parts for an element exist and false when they do not?

Finally, to improve XSLT understanding / skills, can anyone recommend some good learning resources?

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2 answers

Pay attention to this XSLT 1.0 conversion with:

  • AVT (attribute value templates) to simplify attribute definition)
  • one master key used to group an element of the first level.
  • One second composite key to execute sublevel groups

  • widespread use of xsl:apply-templates with modes compared to xsl:for-each

     <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output method="xml" indent="yes"/> <xsl:strip-space elements="*"/> <xsl:key name="kSubs" match="item" use="concat(@id,'|',@sub_id)"/> <xsl:key name="kItems" match="item" use="@id"/> <xsl:template match="i"> <i> <xsl:apply-templates select="item[ generate-id() = generate-id(key('kItems',@id)[1])]"/> </i> </xsl:template> <xsl:template match="item"> <item id="{@id}" name="{@name}" sub_items="{boolean(@sub_id)}"> <xsl:apply-templates select=".|following-sibling::item[ (generate-id() = generate-id(key('kSubs',concat(@id,'|',@sub_id))[1])) and (./@id = current()/@id) ]" mode="sub_id"/> </item> </xsl:template> <xsl:template match="item[@sub_id]" mode="sub_id"> <sub_item sub_id="{@sub_id}" sub_name="{@sub_name}"> <xsl:apply-templates select="key('kSubs',concat(@id,'|',@sub_id))" mode="detail"/> </sub_item> </xsl:template> <xsl:template match="item" mode="detail"> <detail detail_id="{@detail_id}" detail_name="{@detail_name}"/> </xsl:template> </xsl:stylesheet>

Applied to the input specified in your question creates:

 <i> <item id="1" name="one" sub_items="true"> <sub_item sub_id="10" sub_name="s1"> <detail detail_id="t1" detail_name="aaaa"/> <detail detail_id="t2" detail_name="bbb"/> </sub_item> <sub_item sub_id="20" sub_name="s2"> <detail detail_id="t1" detail_name="ccc"/> <detail detail_id="t2" detail_name="ddd"/> </sub_item> </item> <item id="2" name="two" sub_items="true"> <sub_item sub_id="10" sub_name="s1"> <detail detail_id="t1" detail_name="eee"/> <detail detail_id="t2" detail_name="fff"/> </sub_item> <sub_item sub_id="20" sub_name="s2"> <detail detail_id="t1" detail_name="ggg"/> <detail detail_id="t2" detail_name="hhh"/> </sub_item> </item> <item id="3" name="three" sub_items="false"/> <item id="4" name="four" sub_items="true"> <sub_item sub_id="10" sub_name="s1"> <detail detail_id="t1" detail_name="mmm"/> <detail detail_id="t2" detail_name="nnn"/> </sub_item> <sub_item sub_id="20" sub_name="s2"> <detail detail_id="t1" detail_name="ooo"/> <detail detail_id="t2" detail_name="ppp"/> </sub_item> </item> </i>
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Muenchian's method is difficult for nested grouping. The first level of grouping is easy to manage, but for others you need to index elements with compound keys composed with previous identifiers.

 <?xml version="1.0" encoding="UTF-8"?> <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform"> <xsl:output indent="yes" /> <xsl:key name="items" match="item" use="@id" /> <xsl:key name="sub-items" match="item" use="concat(@id, '|', @sub_id)" /> <xsl:template match="i"> <i> <xsl:for-each select="item[generate-id() = generate-id(key('items', @id)[1])]"> <xsl:copy> <xsl:copy-of select="@id|@name" /> <xsl:choose> <xsl:when test="count(key('items', @id)) &gt; 1"> <xsl:attribute name="sub_items">true</xsl:attribute> <xsl:for-each select="key('items', @id)[generate-id() = generate-id(key('sub-items', concat(@id, '|', @sub_id))[1])]"> <sub_item> <xsl:copy-of select="@sub_id|@sub_name" /> <xsl:for-each select="key('sub-items', concat(@id, '|', @sub_id))"> <detail> <xsl:copy-of select="@detail_id|@detail_name" /> </detail> </xsl:for-each> </sub_item> </xsl:for-each> </xsl:when> <xsl:otherwise> <xsl:attribute name="sub_items">false</xsl:attribute> </xsl:otherwise> </xsl:choose> </xsl:copy> </xsl:for-each> </i> </xsl:template> </xsl:stylesheet>
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