> Can anybody tell me the fastest way, how to test, if variable 
> contains some 
> text or number?
> 
> For now, i am using test "string-length($variable)=0", but 
> seems not to be the fastest.

What makes you think it isn't the fastest?

Speed of different operations will vary between processors, but I would be
very surprised if this operation is the cause of your performance
difficulties.

I would recommend writing it as $variable='' since a non-optimizing
processor will otherwise count all the characters in the string, which can
take a while if the string is long and a variable-length character
representation is used (e.g. UTF-8 or UTF-16).

> Somebody tells me to use test "$variable", but with my 
> XalanC, it seems to be true everytime.

That makes me suspect you have declared the variable as

<xsl:variable name="x">
  ...
</xsl:variable>

which means that (contrary to what you said) its value isn't a string or a
number, but a result-tree-fragment, which is likely to be much less
efficient.

Michael Kay
http://www.saxonica.com/