xsl/xalan problem

Hi all,

Consider the following scenario:

+-----------+   +----------------+   +------------+
| Input XML |-->| XSLT Processor |-->| Output XML |
+-----------+   +----------------+   +------------+
                  ^              ^
                  |              |
+----------------+              +-----------------+
|    Input XSL   |              |  Runtime Input  |
+----------------+              +-----------------+

The Output XML depends on three sources:
  1. Input XML
  2. Input XSL
  3. ...and on the Runtime Input

Currently, I am getting the Runtime Input using a specially designed 
extension function. The problem with this approach is that the XSLT 
Processor sometimes calls my extension function too many times. I have 
been told that this may happen if the XSLT Processor decides to optimize 
some of the XSL templates and that I cannot control this behavior. Is 
there a better approach?

Thanks for your help,
Adrian.