Implementing Key Value Concept in XSLT - xslt

Question

I am working on XSLT, where I need to implement something as follows.
My Source XML sample looks like this.
<?xml version="1.0" encoding="ISO-8859-1"?>
<catalog>
<cd>
<title>A</title>
<title>B</title>
<title>C</title>
</cd>
</catalog>
Consider there is some key value pair list is there.
Key Value
A Algebra
B Biology
C Chemistry
D Data Analysis
--- ---
---- ---
I need to write an xslt such that for every occurance of key 'A', need to replace with appropriate value.
I also need to mention the list of Key value pairs in the same XSLT.
Sample Output:
<Data>
<Subject>Algebra</Subject>
<Subject>Biology</Subject>
<Subject>Chemistry</Subject>
</Data>
Can any one help me out how to do it.
Thank you.

Answer 1

I. Simple XSLT 1.0 Solution
This transformation:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:my="my:my">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<my:codes>
<code key="A" value="Algebra"/>
<code key="B" value="Biology"/>
<code key="C" value="Chemistry"/>
<code key="D" value="Data Analysis"/>
</my:codes>
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<xsl:template match=
"title/text()[. = document('')/*/my:codes/*/#key]">
<xsl:value-of select=
"document('')/*/my:codes/*[#key=current()]/#value"/>
</xsl:template>
</xsl:stylesheet>
when applied on the provided XML document:
<catalog>
<cd>
<title>A</title>
<title>B</title>
<title>C</title>
</cd>
</catalog>
produces the wanted, correct result:
<catalog>
<cd>
<title>Algebra</title>
<title>Biology</title>
<title>Chemistry</title>
</cd>
</catalog>
Explanation:
This is the standard way of including inline XML node as a global element (child element of xsl:stylesheet) that belongs to a (non-empty) namespace, different than the xsl namespace.
II. More efficient XSLT 1.0 solution, using keys:
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:my="my:my">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<my:codes>
<code key="A" value="Algebra"/>
<code key="B" value="Biology"/>
<code key="C" value="Chemistry"/>
<code key="D" value="Data Analysis"/>
</my:codes>
<xsl:key name="kCodeByName" match="code" use="#key"/>
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<xsl:template match=
"title/text()[. = document('')/*/my:codes/*/#key]">
<xsl:variable name="vCur" select="."/>
<xsl:for-each select="document('')">
<xsl:value-of select=
"key('kCodeByName', $vCur)/#value"/>
</xsl:for-each>
</xsl:template>
</xsl:stylesheet>
when this transformation is applied on the same XML document (above), the same correct, wanted result is produced:
<catalog>
<cd>
<title value="Algebra"/>
<title value="Biology"/>
<title value="Chemistry"/>
</cd>
</catalog>
Explanation:
Accessing data via the key() function is typically sub-linear -- often O(1) and is extremely faster than linear search (which is important if the number of nodes to be searched is big).
Accessing a node of one document via an index (xsl:key) while processing a node of another document is possible if the document containing the node to be looked-up is the current document. To access nodes from the other document, its root (or node of interest need to be saved and referenced off a variable.)
III. XSLT 2.0 solution:
<xsl:stylesheet version="2.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns:my="my:my">
<xsl:output omit-xml-declaration="yes" indent="yes"/>
<xsl:strip-space elements="*"/>
<xsl:variable name="vCodes">
<codes>
<code key="A" value="Algebra"/>
<code key="B" value="Biology"/>
<code key="C" value="Chemistry"/>
<code key="D" value="Data Analysis"/>
</codes>
</xsl:variable>
<xsl:key name="kCodeByName" match="code" use="string(#key)"/>
<xsl:template match="node()|#*">
<xsl:copy>
<xsl:apply-templates select="node()|#*"/>
</xsl:copy>
</xsl:template>
<xsl:template match=
"title/text()[key('kCodeByName', ., $vCodes)]">
<xsl:sequence select=
"key('kCodeByName', ., $vCodes)/#value"/>
</xsl:template>
</xsl:stylesheet>
when this transformation is applied on the same XML document (above), the same correct, wanted result is produced:
<catalog>
<cd>
<title value="Algebra"/>
<title value="Biology"/>
<title value="Chemistry"/>
</cd>
</catalog>
Explanation:
Almost the same as the efficient XSLT 1.0 solution, but:
In XSLT 2.0 a template match pattern can contain a variable reference.
In XSLT 2.0 there is no need for acrobatic tricks manipulating the current and the indexed documents -- the 3rd argument of the key() function is to specify the tree whose index to use.