I'm trying to insert a release number into my HTML title tag...

I set up the params for release number:

<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:d="http://docbook.org/ns/docbook" xmlns:exsl="http://exslt.org/common" xmlns="http://www.w3.org/1999/xhtml">

    	<xsl:import href="webhelp-book-base.xsl"/>

    	<xsl:param name="product.div.title"> Jack and Jill Cloud Product - </xsl:param>
<!-- test of insertion of release number -->
<xsl:param name="product.rel.number"> 1.0.1 </xsl:param> -->
    	<xsl:param name="product.copyright.string" />
    
</xsl:stylesheet>

then, in webhelp-book-base.xsl - I try to insert "product.rel.number:"


<xsl:template name="head.content">
  <xsl:param name="node" select="."/>
  <xsl:param name="title">
    <xsl:apply-templates select="$node" mode="object.title.markup.textonly"/>
  </xsl:param>

  <title>

    <xsl:value-of select="$product.div.title" />
 	<!-- test of insertion of release number -->
	<xsl:value-of select="$product.rel.number" />

    <xsl:copy-of select="$title"/>

  </title>
  ...
  
  However, in the build I get this compile error:
  
[java] Error at xsl:value-of on line 94 of file://///publishing/hudson/jobs/build-main-documentation/workspace/serverdoc/WorkingDoc/main/publishing/docbook-xsl-customization/webhelp-book-base.xsl:
[java]   Variable product.rel.number has not been declared
[java] Transformation failed: Failed to compile stylesheet. 1 error detected.

If I remove the "product.rel.number" attempt, the build goes back to working like before (Producing a title tag with product name and book title

I'm not sure how I would achieve the result I want in the built HTML:

<title xmlns:d="http://docbook.org/ns/docbook">Jack and Jill Cloud Product - 1.0.1 - Jack and Jill go up the hill</title>

Rob Flynn
Principal Technical Writer