Basic usage of types

      <xsl:stylesheet
                  xmlns:sch="http://www.w3.org/2001/XMLSchema"
                  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                  version="2.0"
                  exclude-result-prefixes=" sch">
            <xsl:output  method="xml"
                        indent="yes"
                        omit-xml-declaration="yes"/>

            <xsl:template  name="xxx">
                  <xsl:param  name="a"
                              as="sch:integer"/>
                  <xsl:value-of  select="$a * $a * $a"/>
            </xsl:template>

            <xsl:template  match="/aaa">
                  <xsl:call-template  name="xxx">
                        <xsl:with-param  name="a"
                                    as="sch:integer"
                                    select="bbb"/>
                  </xsl:call-template>
            </xsl:template>

      </xsl:stylesheet>

      <aaa>
            <bbb>1.34</bbb>
      </aaa>

Error: