Is it possible to test if a child (or grand-child) element of the current node exists (within an xsl:if or :when expression)? If so, how?

Test for the existence of a child element named "foo":
 <xsl:if test="foo">
Test for a grandchild:
 <xsl:if test="*/foo">
Background: The expressions select a node set, which is
implicitely converted to boolean false if empty and
boolean true if non-empty.
Of course, you may also use
 test="count(foo) &gt; 0"
and similar expressions.

HTH
J.Pietschmann