Customization of attribute set

[julia.jacobson@arcor.de]

Hello everybody out there using DocBook 5,

Customizing the attribute set "section.title.properties" does not work for my minimal example:

my_doc.xml:
<?xml version="1.0" encoding="utf-8"?>
<article xmlns="http://docbook.org/ns/docbook"; version="5.0" xml:lang="en">
  <title>Sample article</title>
  <section>
    <title>Sample section</title>
  </section>
  <para>This is a very short article.</para>
</article>

my_style.xls:
<?xml version="1.0"?>
<xsl:stylesheet 
     xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
     xmlns:fo="http://www.w3.org/1999/XSL/Format";
     xmlns:d="http://docbook.org/ns/docbook";
     exclude-result-prefixes="d"
     version="1.0">
<xsl:import href="http://docbook.sourceforge.net/release/xsl/current/html/docbook.xsl"/>
<xsl:attribute-set name="section.title.properties">
  <xsl:attribute name="text-align">center</xsl:attribute>
</xsl:attribute-set>
</xsl:stylesheet>

Toolchain: xsltproc -o output.html my_style.xls my_doc.xml
I would expect the title of the section to be centered, but this is not the case.
Could you please point me towards additional diagnostics to run in order to pin down the problem?

Kind regards,
Julia