Dear Sirs
I'm trying to produce a PDF from a docbook xml file. I need to use a customization layer but I keep receiving an error message like this:
[Saxon6.5.5] ERROR: Document root element for FO output must be one of the following elements: appendix article bibliography book chapter colophon dedication glossary index part preface qandaset refentry reference sect1 section set setindex
and
SystemID: /Users/Sandro/Documents/quaderni_storicamente/index.xml
Engine name: Saxon6.5.5
Severity: error
Description: Cannot apply cascading transformation. Reason: Processing terminated by xsl:message at line 207

Here is the xsl
<?xml version='1.0'?>
<xsl:stylesheet
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:fo="http://www.w3.org/1999/XSL/Format"
    version="1.0">
    <xsl:import href="fo/docbook.xsl"/>
    <xsl:template match="/book/chapter/para[@role = 'intro']">
        <fo:block border="0.5pt solid blue"
            padding="3pt"
            xsl:use-attribute-sets="normal.para.spacing">
            <xsl:apply-templates/>
        </fo:block>
    </xsl:template>
</xsl:stylesheet>

Thank you in advance

Claudio