Separators

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

            <xsl:template  match="/aaa">
                  <xsl:value-of  separator="-">
                        <ooo>1</ooo>
                        <xsl:value-of  select="2"/>
                        <zzz>3</zzz>
                  </xsl:value-of>
            </xsl:template>

      </xsl:stylesheet>

      <aaa/>

1-2-3