Template Instructions

xsl:apply-templates
Find correct template to apply
xsl:value-of
Evaluates select and outputs value
xsl:text
Outputs text
xsl:copy
Copy target node from source to output
xsl:copy-of
Complete tree copy
xsl:for-each
Applies same template to multiple document nodes
xsl:choose
Conditional testing with otherwise and when
xsl:if
Conditional test
xsl:call-template
Calls a named template
xsl:document
Creates a new output file
xsl:element
Generates an element in the output with specified name
xsl:attribute
Generates attribute node and applies to element
xsl:cdata
Outputs a CDATA section in the output
xsl:variable
Defines a local or global variable

xsl:copy

<xsl:copy>

Copies the current node from the Source Tree to the Result Tree

Note: it does not copy the contents of the node, just the node itself 

<?xml version='1.0'?>
<xsl:stylesheet xmlns:xsl = "http://www.w3.org/1999/XSL/Transform" version = "1.0" >
<xsl:output method="xml" indent="no"/> Puts an XML declaration 
                                          on the output, no indentation
<xsl:template match="*" >   Matches any node in the XML tree
<xsl:copy>                  Copy this node to the output tree
<xsl:apply-templates />     Apply any templates to the  node's children
</xsl:copy>
</xsl:template>
</xsl:stylesheet>

xsl:copy-of

For copying the whole tree, rather than specific nodes, to the output, use xsl:copy-of:

<xsl:template match="thought" >
 <xsl:copy-of select="."/>
</xsl:template>

thought node, its attributes, its descendants and all their attributes are copied to the output tree

xsl:for-each

<xsl:for-each select="...">
  • Selects a set of nodes for processing
  • Performs the same processing on each node in the node-set
  • The nodes in the node-set are processed in document order unless sort instructions appear
    • Document order is the order of traversal of the tree
    • A node comes before its attributes
    • Its attributes come before its children
    • No order of attributes is defined
  • Template actively defines the order in which processing takes place
  • A single template creates the complete Output Tree

Here is an example of an XML file:

  • Many XML documents contain multiple records that are similar
  • Templates need to be applied to all or some of these
<cdlist>
<cd>
  <artist>Aatabou, Najat</artist>
  <title>The Voice of the Atlas</title>
  <label></label>
  <catalog>CDORBD 069</catalog>
  <filed>C05 World</filed>
  <playlist>
    <work>Baghi narajah</work>
    <work>Finetriki</work>
    <work>Shouffi rhirou</work>
    <work>Lila ya s'haba</work>
    <work>Ouardatte lajnane</work>
    <work>Ditih</work>
  </playlist>
</cd>
- - -
</cdlist>

xsl:for-each

<xsl:template match="cdlist">  The context node
 <xsl:for-each select="cd">   Each cd becomes the current node in turn
  <hr />
  <h2> <xsl:value-of select="artist"/></h2> child of current node
  <h2><xsl:value-of select="title"/></h2>
  <table summary="cd stats" width="80%">
   <col width="20%" /><col width="20%" /><col width="20%" /><col width="20%" />
   <thead>
   <tr><th>Label</th><th>Catalog Number</th><th>Stored At</th></tr>
   </thead><tbody>
   <tr>
    <td><xsl:value-of select="label"/></td>
    <td><xsl:value-of select="catalog"/></td>
    <td><xsl:value-of select="filed"/></td>
   </tr>
  </tbody></table>
 <h3>Playlist</h3>
 <ul>
  <xsl:for-each select="playlist/work">  Each work is the current node in turn
  <li><xsl:value-of select="." /></li>
  </xsl:for-each>
 </ul>
 </xsl:for-each>
 <hr />
</xsl:template>

Sorting

<xsl:sort select="xxx" order="" case-order="" data-type=""/>

  • Instead of document order, specifies a different order for processing child nodes
  • Can be a child of xsl:apply-templates or xsl:for-each
  • Within xsl:for-each it must be before any other instructions
  • Several xsl:sort are allowed and the first is the major sort, the minor sort on the next and so on
  • select attribute defines the sort key. Default is the text value of the node-set selected
  • order can have values ascending or descending
  • case-order can have values upper-first or lower-first
  • data-type can have values text or number to decide whether values are sorted alphabetically or numerically. Default is alphabetic
  • data-type="text" puts 10 before 5 while data-type="number" puts 5 before 10
  • The select value can be complex and include doing arithmetic so this is a sophisticated operation

xsl:if

<xsl:if test=".." >
. . .
</xsl:if>
  • Contents of <xsl:if> element only obeyed if test is true:
    • If test result is a node-set, true if node-set contains one or more nodes
    • If test result is a string, true if string is non-empty
    • If test result is a number, true if value is non-zero
    • If test result is a truth value, depends on the truth value
  • Only CDs satisfying the test are retained 
    <xsl:template match="cdlist">
<xsl:for-each select="cd">
<xsl:if test="filed[. = 'C05 World']">
<tr>
<td style="color:blue;font-weight:bold"><xsl:value-of select="artist"/></td>
<td style="color:red;font-weight:bold"><xsl:value-of select="title"/></td>
<td style="color:darkgray;font-weight:bold"><xsl:value-of select="filed"/>
</td>
</tr>
</xsl:if>
</xsl:for-each>
</xsl:template>

Filtering via <xsl:choose>

<xsl:choose>
  <xsl:when test=".."> ... </xsl:when>
  <xsl:when test=".."> ... </xsl:when>
  <xsl:otherwise> . . .    </xsl:otherwise>
</xsl:choose>
  • xsl:choose provides either or processing
  • Set of xsl:when elements tested in order
  • If none match, xsl:otherwise is obeyed

For example, colour code the different types of CD

Colour Code the CDs

<xsl:for-each select="cd">
  <tr>
  <xsl:choose>
    <xsl:when test="filed[. = 'C05 World']">
      <td style="color:red">
        <xsl:value-of select="artist"/>
      </td>
      <td>
        <xsl:value-of select="title"/>
      </td>
    </xsl:when>
<xsl:when test="filed[. = 'C06 Country']"><td style="color:blue">...</xsl:when>
<xsl:when test="filed[. = 'C11 Jazz Trad']"><td style="color:green">...</xsl:when>
<xsl:when test="filed[. = 'C20 Fado']"><td style="color:violet">...</xsl:when>
<xsl:when test="filed[. = 'C01 Pop']"><td style="color:gray">...</xsl:when>
<xsl:when test="filed[. = 'C07 Cajun']"><td style="color:brown">...</xsl:when>
<xsl:when test="filed[. = 'C03 Jazz Vocal']"><td style="color:yellow">...
</xsl:when>
<xsl:otherwise><td style="color:black">...</xsl:otherwise>
</xsl:choose>
  </tr>
</xsl:for-each>

There are other XSLT instructions but these give a flavour of what you can do.