How do I check for the existence of an external file with XSL?

Question

I\'ve found a lot of examples that reference Java and C for this, but how do I, or can I, check for the existence of an external file with XSL.

First, I realize that

Answer 1

In case someone else needs it and is using fop, I would like to share this answer since it worked for me like a charm.

I've found a solution:

and it works independently of XSLT 1.0 or 2.0