Sorting according to case

      <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="/">
                  <upper>
                        <xsl:apply-templates  select="/aaa/bbb">
                              <xsl:sort  case-order="upper-first"/>
                        </xsl:apply-templates>
                  </upper>
                  <lower>
                        <xsl:apply-templates  select="/aaa/bbb">
                              <xsl:sort  case-order="lower-first"/>
                        </xsl:apply-templates>
                  </lower>
                  <default>
                        <xsl:apply-templates  select="/aaa/bbb">
                              <xsl:sort/>
                        </xsl:apply-templates>
                  </default>
            </xsl:template>

            <xsl:template  match="bbb">
                  <bbb>
                        <xsl:value-of  select="."/>
                  </bbb>
            </xsl:template>

      </xsl:stylesheet>

      <aaa>
            <bbb>a</bbb>
            <bbb>b</bbb>
            <bbb>A</bbb>
            <bbb>B</bbb>
      </aaa>

      <upper>
            <bbb>A</bbb>
            <bbb>a</bbb>
            <bbb>B</bbb>
            <bbb>b</bbb>
      </upper>
      <lower>
            <bbb>a</bbb>
            <bbb>A</bbb>
            <bbb>b</bbb>
            <bbb>B</bbb>
      </lower>
      <default>
            <bbb>a</bbb>
            <bbb>A</bbb>
            <bbb>b</bbb>
            <bbb>B</bbb>
      </default>