Processor details:
Name: org/apache/xalan
Comment: Main Xalan engine implementing TrAX/JAXP
Specification-Title: Java API for XML Processing
Specification-Vendor: Sun Microsystems Inc.
Specification-Version: 1.2
Implementation-Title: org.apache.xalan
Implementation-Version: 2.6.0

Anyway, I could really use some help or guidance here. I have two sets of nodes that are intermixed - I need to output them ordered by a sort order attribute, and group them by a key attribute such that the key only shows up when it changes from the previously sorted item. Here's a simplified example:

Test.xml:
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet href="Test.xsl" type="text/xsl"?>

<root>
                <red order="1" key="F" text="red 1 B" />
                <red order="3" key="F" text="red 3 B" />
                <red order="4" key="C" text="red 4 C" />
                <red order="6" key="D" text="red 6 D" />
                <red order="9" key="E" text="red 9 E" />
                <red order="10" key="F" text="red 10 F" />
                <blue order="2" key="B" text="blue 2 B" />
                <blue order="5" key="D" text="blue 5 D" />
                <blue order="7" key="D" text="blue 7 D" />
                <blue order="8" key="E" text="blue 8 E" />
                <blue order="11" key="F" text="blue 11 F" />
                <blue order="12" key="G" text="blue 12 G" /> </root>

Expected output:
F:
red 1 B
B:
blue 2 B
F:
red 3 B
C:
red 4 C
D:
blue 5 D
red 6 D
blue 7 D
E:
blue 8 E
red 9 E
F:
red 10 F
blue 11 F
G:
blue 12 G

<xsl:stylesheet
  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
  xmlns:exsl="http://exslt.org/common"
  exclude-result-prefixes="exsl"
  version="1.0">

  <xsl:template match="blue | red">
    <xsl:if test="not(preceding-sibling::*[1]/@key = @key)">
      <xsl:value-of select="concat(@key, $nl)"/>
    </xsl:if>
    <xsl:value-of select="concat(@text, $nl)"/>
    <xsl:apply-templates select="following-sibling::*[1]"/>
  </xsl:template>

	Martin Honnen
	http://msmvps.com/blogs/martin_honnen/