XSLT transformation to xml, grouping by key

Question

I have problem with write xsl to transform my xml to raport version. It looks like that:

    
        Jo         


        

Answer 1

This transformation:

<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="kArticleById" match="article"
  use="authorId"/>

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

 <xsl:template match="/*">
  <raport>
        <xsl:apply-templates select="authors/author"/>
  </raport>
 </xsl:template>

 <xsl:template match="author">
  <authorArticles>
  <xsl:call-template name="identity"/>
    <articles>
      <xsl:apply-templates select="key('kArticleById',@id)"/>
    </articles>
  </authorArticles>
 </xsl:template>

 <xsl:template match="title">
  <xsl:apply-templates/>
 </xsl:template>
 <xsl:template match="author/@id|articles|authorId"/>
</xsl:stylesheet>

when applied on the provided XML document:

<library>
    <authors>
        <author id="1001">John</author>
        <author id="1002">Tom</author>
    </authors>
    <articles>
        <article>
            <authorId>1001</authorId>
            <title>Article1</title>
        </article>
        <article>
            <authorId>1002</authorId>
            <title>Article2</title>
        </article>
        <article>
            <authorId>1001</authorId>
            <title>Article3</title>
        </article>
    </articles>
</library>

produces the wanted, correct result:

<raport>
   <authorArticles>
      <author>John</author>
      <articles>
         <article>Article1</article>
         <article>Article3</article>
      </articles>
   </authorArticles>
   <authorArticles>
      <author>Tom</author>
      <articles>
         <article>Article2</article>
      </articles>
   </authorArticles>
</raport>

Notes:

1. Use/overriding of the identity rule.

2. All articles with the same authorId are selected using keys. This is significantly more efficient in case of many authors with many articles.

Answer 2

This XSLT:

<?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"/>

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

<xsl:template match="library">
    <raport>
        <xsl:apply-templates select="authors/author"/>
    </raport>
</xsl:template>

<xsl:template match="author">
    <authorArticles>
        <xsl:call-template name="identity"/>
        <articles>
            <xsl:apply-templates select="../../articles/article[authorId = current()/@id]"/>
        </articles>
    </authorArticles>
</xsl:template>

<xsl:template match="article">
    <xsl:call-template name="identity"/> <!-- In case of more characteristics -->
</xsl:template>

<xsl:template match="title">
    <xsl:value-of select="."/>
</xsl:template>

<xsl:template match="author/@id | authorId"/>

</xsl:stylesheet>

With this XML input:

<library>
<authors>
    <author id="1001">John</author>
    <author id="1002">Tom</author>
</authors>
<articles>
    <article>
        <authorId>1001</authorId>
        <title>Article1</title>
    </article>
    <article>
        <authorId>1002</authorId>
        <title>Article2</title>
    </article>
    <article>
        <authorId>1001</authorId>
        <title>Article3</title>
    </article>
</articles>
</library>

Provides this needed result:

<raport>
    <authorArticles>
       <author>John</author>
       <articles>
          <article>Article1</article>
          <article>Article3</article>
       </articles>
    </authorArticles>
    <authorArticles>
       <author>Tom</author>
       <articles>
           <article>Article2</article>
       </articles>
    </authorArticles>
</raport>

The further optimization might be using keys, but it looks premature with your structure.