Hi, Eucaly61

Currently, I am thinking of a "text classification" application,
if that possible that I can use POPfile as a "Text Classification Engine" -- training to classify some user given "text" with command line or application interface, and so on ...

I think you can use the XMLRPC interface of POPFile.
For more information, please see:

http://getpopfile.org/docs/popfilemodules:xmlrpc

But since POPFile will parse the text as an e-mail message, you may be required to add some 'dummy mail headers' to the text file.

For example:

---
Subject: the text's title

the content of the text....
---

Naoki