[Boost-users] What does "RALL-style" means ?

Hi, everyone. When I refer the document of thread library, a word "RALL-style" appear in the introduction of the class lock_guard: This provides simple RAII-style locking of a Lockable object, to facilitate exception-safe locking and unlocking. I didn't got the main point of this word "RALL-style", could anyone tell me the meaning ? Thanks. Best wishes.