Unwanted xmlns attribute appearing

Hello,

   I am generating RSS feeds from an HTML file. With Perl, until I finally realized XSLT would be a much better solution. I decided to create a new XML file, and to have seceral XSL stylesheets, one to produce the HTML file and the others to produce the RSS files. First question: was that stupid?

   The XML file is currently looking like this: http://edhel.gimp.org/devnews.xml
   I managed to write the XSL to produce HTML: http://edhel.gimp.org/devnews.xsl produces http://edhel.gimp.org/devnews.html

   Now I'm struggling with the RSS1.0 feed. http://edhel.gimp.org/devnews-rss1.xsl produces http://edhel.gimp.org/devnews-rss1.xml
   The <item> markup gets a xmlns="" attribute, and I don't know where that comes from.

<xsl:template match="week">
  <item>
    <xsl:attribute name="rdf:about">http://edhel.gimp.org/devnews.html#<xsl:value-of select="normalize-space(parent::year/text())"/>-<xsl:value-of select="normalize-space(text())"/></xsl:attribute>
    [...]
  </item>
</xsl:template>

produces:

<item xmlns="" rdf:about="http://edhel.gimp.org/devnews.html#2006-17">

   So, second question: what did I miss there?

   Thanks,
Karine