Randomize XML with xsltproc

Question

I have a simple xml file:

<headlines>
  <headline>
  ...
  </headline>
  <headline>
  ...
  </headline>
  <headline>
  ...
  </headline>
</headlines>

All I want to do is shuffle the order in which headlines appear. I've been fooling around how this template should look, but I can't get it working.

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:template match="/headline">
<xsl:for-each select="headline">
  __not sure what to do here? rand() isn't a thing?__

Answer 1

One way to do this would be to use the function generate-id() as a sorting criterion. Suppose you have the following input:

<?xml version="1.0" encoding="ISO-8859-1"?>
<headlines>
  <headline>
    Limburg
  </headline>
  <headline>
    Fukushima
  </headline>
  <headline>
    Große Koalition
  </headline>
  <headline>
    Flugzeugabsturz
  </headline>
</headlines>

With this XSLT you can "randomize" the output:

<?xml version="1.0" encoding="ISO-8859-1"?>
<xsl:stylesheet 
    version="1.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

  <xsl:output method="xml" encoding="ISO-8859-1"/>

  <xsl:template match="/headlines">
    <headlines>

      <xsl:for-each select="headline">
        <xsl:sort select="generate-id(.)"/>

        <headline id="{generate-id(.)}">
          <xsl:copy-of select="./text()"/>
        </headline>

      </xsl:for-each>

    </headlines>
  </xsl:template>
</xsl:stylesheet>

The result is

<?xml version="1.0" encoding="ISO-8859-1"?>
<headlines><headline id="idm3928">
    Limburg
  </headline><headline id="idm5512">
    Flugzeugabsturz
  </headline><headline id="idm5704">
    Große Koalition
  </headline><headline id="idm5920">
    Fukushima
  </headline></headlines>

Three things should be noted:

• The output of attribute "id" in the headline tag is not necessary. This is just for visualizing the sort criterion.
• The sorting order depends on the xslt processor used (in this case a Debian xsltproc).
• It's not really "random". However, the processor xsltproc actually chooses new ids with every call so in fact the headlines get "shuffled". :-)