sample xsl to validate XML against XSD

[mnbv]

Hi ,
I am totally new to XSLs, trying to write an xsl(JDeveloper) to validate XML against a given schema.
I have been trying with the following but getting a syntax not supported error for "instance of schema-element"

Can someone provide a sample xsl to validate xml against the schema?

<?xml version="1.0" encoding="windows-1252" ?>
<xsl:stylesheet version="2.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:import-schema schema-location="po1.xsd"/>
<xsl:output method="xml" version="1.0" indent="yes"/>
<!-- Root template -->
<xsl:template match="/">
<xsl:if test="not(* instance of schema-element(provisionning))">

   <xsl:message terminate="yes">
      Source document does not have valid structure
   </xsl:message>

</xsl:if>
<xsl:apply-templates/>
</xsl:template>

</xsl:stylesheet>

Thanks in advance
mnbv