How do I name output files based on files processed from a watched folder?

Hello!

I've built a small process to merge XML files with XDP templates, generating PDF files at the end of the process.

Right now the process is generating all files with a fixed name + a random number, as defined in the Input panel (literal value with option "Appen a suffix..." checked.

I'd like to change this so the resulting files have the same name as the input files, changing only the extension (PDF instead of XML).

I believe I should change from literal value to XPath expression, in order to build the resulting name based on the input file name.

QUESTION: what function should I use to get the input file name in XPath builder (if this is the right place to do it) ?

I tried with:

     getDocAttribute(/process_data/@docApolicesXML,"wsfilename")  + ".PDF"

Does not work.

Thanks a lot for any hints!

Marcos