PAM and conversation functions

[Kala B]

Hi,
The PAM framework expects the applications to handle user interactions
( hence the conversation function is provided by the application). For
advanced authentication, depending on the type, the PAM module needs
to collect appropriate information. So, say, if we have a PAM module
for fingerprint authentication, it need not collect any user input
(like password) but needs to interact with the user through some
hardware. An application developer would have provided a generic
conversation function. The adminstrator could change the backend PAM
modules to any advanced authentication.

How does PAM framework support such mechanisms? 

Thanks
Kala B