XPATH Axes - Issues - xslt

Question

XML structure:
<units>
<unit>
<lesson>
<name>Sample 1</name>
<sections>
<section type="IN">
<title> Sample Title 1 </title>
</section>
</sections>
</lesson>
<lesson>
<name>Sample 2</name>
<sections>
<section type="OF">
<title> Sample Title 2 </title>
</section>
</sections>
</lesson>
<lesson>
<name>Sample 3</name>
<sections>
<section type="IN">
<title> Sample Title 3</title>
</section>
</sections>
</lesson>
<lesson>
<name>Sample 4</name>
<sections>
<section type="AS">
<title> Sample Title 4</title>
</section>
</sections>
</lesson>
<lesson>
<name>Sample 5</name>
<sections>
<section type="IN">
<title> Sample Title 5</title>
</section>
</sections>
</lesson>
</unit>
</units>
My requirement is to get the values of title element and display as follows (Grouping similar data and display)
IN:
Sample Title 1
Sample Title 3
Sample Title 5
OF:
Sample Title 2
AS:
Sample Title 5
I have used following-sibling option to get the expected output. Since the XML structure is huge(I have pasted only the snippet), I cannot hard-code the path using ../../ and all in XSLT. Please help me in getting the expected output.

Answer 1

It's better to solve this using grouping than either of the sibling axes:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text" />
<xsl:key name="bySectionType" match="section" use="#type" />
<xsl:template match="/">
<xsl:apply-templates select="units/unit/lesson/sections/section" />
</xsl:template>
<xsl:template match="section" />
<xsl:template
match="section[generate-id()=
generate-id(key('bySectionType', #type)[1])]">
<xsl:value-of select="concat(#type, ':
')" />
<xsl:apply-templates select="key('bySectionType', #type)" mode="out" />
</xsl:template>
<xsl:template match="section" mode="out">
<xsl:value-of select="concat(normalize-space(title), '
')" />
</xsl:template>
</xsl:stylesheet>
Output:
IN:
Sample Title 1
Sample Title 3
Sample Title 5
OF:
Sample Title 2
AS:
Sample Title 4
For completeness, the following stylesheet achieves the same result using the preceding and following axes:
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text" />
<xsl:template match="/">
<xsl:apply-templates select="units/unit/lesson/sections/section" />
</xsl:template>
<xsl:template match="section" />
<xsl:template
match="section[not(preceding::section[#type=current()/#type])]">
<xsl:value-of select="concat(#type, ':
')" />
<xsl:apply-templates select=".|following::section[#type=current()/#type]"
mode="out" />
</xsl:template>
<xsl:template match="section" mode="out">
<xsl:value-of select="concat(normalize-space(title), '
')" />
</xsl:template>
</xsl:stylesheet>
This is a far less efficient solution. The normal way to solve this is with the Muenchian Method for grouping, as shown above.

Answer 2

Here is the solution in XSLT 2.0:
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="text" />
<xsl:template match="/">
<xsl:for-each-group select="//section" group-by="#type">
<xsl:value-of select="#type, ':
'" separator=""/>
<xsl:value-of select="current-group()/title" separator="
" />
<xsl:value-of select="'
'"/>
</xsl:for-each-group>
</xsl:template>
</xsl:stylesheet>