XSLT: Sort by multiple items

Question

I have XML data such as:

<feed>
  <entry>
    <id>4</id>
    <updated>2011-01-18T16:55:54Z</updated>
    <title>title2</title>
  </entry>
  <entry>
    <id>3</id>
    <updated>2011-01-18T16:55:54Z</updated>
    <title>title1</title>
  </entry>
  <entry>
    <id>2</id>
    <updated>2011-01-18T16:55:54Z</updated>
    <title>title1</title>
  </entry>
  <entry>
    <id>1</id>
    <updated>2011-01-18T16:55:54Z</updated>
    <title>title</title>
  </entry>
</feed>

And I need the outcome to result like:

<feed>
  <entry>
    <id>1</id>
    <updated>2011-01-18T16:55:54Z</updated>
    <title>title</title>
  </entry>
  <entry>
    <id>2</id>
    <updated>2011-01-18T16:55:54Z</updated>
    <title>title1</title>
  </entry>
  <entry>
    <id>3</id>
    <updated>2011-01-18T16:55:54Z</updated>
    <title>title1</title>
  </entry>
  <entry>
    <id>4</id>
    <updated>2011-01-18T16:55:54Z</updated>
    <title>title2</title>
  </entry>
</feed>

Basically I need the XSLT to sort on the title, then the ID. I have made an XSLT but the shorter times come out last (using Xerces):

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet xmlns:atom="http://www.w3.org/2005/Atom"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0">
<xsl:output method="xml" encoding="UTF-8" indent="yes" />

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

 <xsl:template match="atom:feed">
  <xsl:copy>
   <xsl:apply-templates select="*" />
   <xsl:for-each select="atom:entry">
    <xsl:sort select="string-length(atom:title)" order="descending" />
    <xsl:sort select="atom:title" data-type="text" order="ascending" />
    <xsl:copy-of select="."/>
   </xsl:for-each>
  </xsl:copy>
 </xsl:template>

 <xsl:template match="atom:feed/atom:entry"/>

</xsl:stylesheet>

Answer 1

For your input sample (not actually an Atom feed), this stylesheet:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="@*|node()">
        <xsl:copy>
            <xsl:apply-templates select="@*|node()" />
        </xsl:copy>
    </xsl:template>
    <xsl:template match="feed">
        <xsl:copy>
            <xsl:apply-templates>
                <xsl:sort select="update" order="descending"/>
                <xsl:sort select="title"/>
                <xsl:sort select="id" data-type="number"/>
            </xsl:apply-templates>
        </xsl:copy>
    </xsl:template>
</xsl:stylesheet>

Output:

<feed>
    <entry>
        <id>1</id>
        <updated>2011-01-18T16:55:54Z</updated>
        <title>title</title>
    </entry>
    <entry>
        <id>2</id>
        <updated>2011-01-18T16:55:54Z</updated>
        <title>title1</title>
    </entry>
    <entry>
        <id>3</id>
        <updated>2011-01-18T16:55:54Z</updated>
        <title>title1</title>
    </entry>
    <entry>
        <id>4</id>
        <updated>2011-01-18T16:55:54Z</updated>
        <title>title2</title>
    </entry>
</feed>

Note: This date time format can be ordered like string (default) as long as there is no different time zone.