samples/ExternalFunction/foo.xsl

<?xml version="1.0"?> 
<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="1.0"
				xmlns:external="http://ExternalFunction.xalan-c++.xml.apache.org"
        exclude-result-prefixes="external">

  <xsl:template match="area">
    <xsl:choose>
	  <xsl:when test="function-available('external:square-root') and function-available('external:cube')"> 
        <given>
          The area of each face of the cube is <xsl:value-of select="@value"/>
          <xsl:text> square units </xsl:text> <xsl:value-of select="@units"/>. 
        </given>    
        <result>
          Accordingly, the length of each side is <xsl:value-of select="external:square-root(@value)"/>
          <xsl:text> </xsl:text><xsl:value-of select="@units"/> and the volume of the cube is 
          <xsl:value-of select="external:cube(external:square-root(@value))"/>
          <xsl:text> cubic </xsl:text> <xsl:value-of select="@units"/>.
        </result>
	  </xsl:when>
	  <xsl:otherwise>
        <result>
		  The functions external:square-root() and external cube() are not available!
		</result>
	  </xsl:otherwise>
    </xsl:choose>
  </xsl:template>

  <xsl:template match="now">       
    <xsl:choose>
	  <xsl:when test="function-available('external:asctime')"> 
        <when>
          Date and time when we figured all this out: <xsl:value-of select="external:asctime()"/>.
        </when>
	  </xsl:when>
	  <xsl:otherwise>
        <result>
		  The function external:asctime() is not available!
		</result>
	  </xsl:otherwise>
    </xsl:choose>
  </xsl:template>

</xsl:stylesheet>