[xsl] XSLT File I/O?

["Hiral Parikh" <hparikh@xxxxxxxxxxxxxxxx>]

Hi,
I am doing a bunch of XSL transformations from an XML file using Cocoon and
finally generate a FO file. 

I have the following requirement to carry out in my XSL transformations:
1. Get the fileurl for images in the XML (e.g. /images/A.jpg)
2. Check for the file on a physical location
3. If the file exist then ok, otherwise change the file url
(/images/A_temp.jpg).

I have not used File I/O using XSL and am not even sure if that's possible. 
Can someone please throw some light on this ? 
Is it possible to fulfill the above requirement using XSL? Are there any
other ways to do this using Cocoon?

Thanks in advance,
Hiral