xsl:choose element is used to choose one of a number of alternative outputs. The element
typically contains a number of xsl:when elements, each with a separate test condition. The first
xsl:when element whose condition matches the current element in the source document is expanded, the others
are ignored. If none of the conditions is satisfied, the xsl:otherwise child element, if any, is
The test condition in the
xsl:when element is a boolean expression.
The full syntax of expressions is outlined in XPath Expression Syntax.