Declaration of stylesheet functions

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

            <xsl:function  name="my:printHello">
                  <xsl:text>Hello</xsl:text>
            </xsl:function>

            <xsl:function  name="my:printWorld">
                  <xsl:text>world</xsl:text>
            </xsl:function>

            <xsl:template  match="/aaa">
                  <xsl:value-of  select="my:printHello()"/>
                  <xsl:text>, </xsl:text>
                  <xsl:value-of  select="my:printWorld()"/>
                  <xsl:text>!</xsl:text>
            </xsl:template>

      </xsl:stylesheet>

      <aaa/>

Hello, world!