There are four levels of interaction between an application and the session handler.

• level 0 - JACK application is not linked to a session handling library (liblash, libladish). User has to save application projects manually or rely on autosave support from application.
• level 1 - JACK application is not linked to a session handling library (liblash, libladish). Application saves on request through UNIX signal.
• level 2 - JACK application is linked to liblash. Limited interaction with session handler because of liblash API limitations.
• level 3 - JACK application is linked to libladish. Full interaction with session handler. Query room virtual ports.