Question about xsl-xslt

Dear all,

I'm new in xml world so pease forgive me if my question is a silly one
I'd like to define and test a variable in my xslt stylesheet but it
didn't work:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0"
xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output method="xml" version="1.0" encoding="UTF-8" indent="yes"/>
 <xsl:template match="/">
 <xsl:variable name="level" select="3"></xsl:variable>
                 <xsl:choose>
                    <xsl:when test="$level=3">
                        <xsl:value-of select="/filevideo/campi/campo1">
                        </xsl:value-of>
                    </xsl:when>
                 </xsl:choose>
</xsl:template>

It doesn't work because xslt doesn't recognize xsl:choose and xsl:when
which belengs to xsl namespace?
How may I make it work? I have to define two namespace in my xml
document or what?

Please any comment is well accepted
Thanks in advance
Saverio



 XSL-List info and archive:  http://www.mulberrytech.com/xsl/xsl-list