Difference between empty and not available elements

Hi,

data parsed by my xsl sometimes has empty elements, say <x/>

In my xsl i have the following code:

<xsl:if test="x">
	do something

test is true for empty the above empty element an something like
<x><y>text</y></x>

Something like "and x=!''" doesn't work because text isn't always
present.

Any ideas?

Best regards
Thomas.