Question: Is it possible to use the <xsl:otherwise> element as the false alternative to an <xsl:if> element?
Answer: No, the <xsl:otherwise> element is used inside an <xsl:choose> wrapper in conjunction with one or more <xls:when> elements.
Answer: No. The <xls:script> tag is used to define global entities, so if you want the function to be globally accessible, it cannot be defined locally.
Question: What's the main advantage of using a set of <xls:when> elements rather than a set of <xls:if> elements?
Answer: The <xls:when> elements allow for the <xsl:otherwise> or "none of the above" option. Because the available options may expand or be combined, there's greater flexibility when you use <xls:when>.