XSL element otherwise

Conditional Processing with xsl:choose

<choose>
Model: (when+, otherwise?)
</choose>

<when>
  test = boolean-expression
Model: template
</when>

<otherwise>
Model: template
</otherwise>

The xsl:choose element selects one among a number of possible alternatives. It consists of a sequence of xsl:when elements followed by an optional xsl:otherwise element. Each xsl:when element has a single attribute, test, which specifies an expression. The content of the xsl:when and xsl:otherwise elements is a template. When an xsl:choose element is processed, each of the xsl:when elements is tested in turn, by evaluating the expression and converting the resulting object to a boolean as if by a call to the boolean function. The content of the first, and only the first, xsl:when element whose test is true is instantiated. If no xsl:when is true, the content of the xsl:otherwise element is instantiated. If no xsl:when element is true, and no xsl:otherwise element is present, nothing is created.

The following example enumerates items in an ordered list using arabic numerals, letters, or roman numerals depending on the depth to which the ordered lists are nested.

<xsl:template match="orderedlist/listitem">
  <fo:list-item indent-start='2pi'>
    <fo:list-item-label>
      <xsl:variable name="level"
                    select="count(ancestor::orderedlist) mod 3"/>
      <xsl:choose>
        <xsl:when test='$level=1'>
          <xsl:number format="i"/>
        </xsl:when>
        <xsl:when test='$level=2'>
          <xsl:number format="a"/>
        </xsl:when>
        <xsl:otherwise>
          <xsl:number format="1"/>
        </xsl:otherwise>
      </xsl:choose>
      <xsl:text>. </xsl:text>
    </fo:list-item-label>
    <fo:list-item-body>
      <xsl:apply-templates/>
    </fo:list-item-body>
  </fo:list-item>
</xsl:template>