A History Keeping Debugging System for PLASMA

Abstract

PLASMA (for PLAnner-like System Modeled on Actors) is a message-passing computer language based on actor semantics. Since every event in the system is the receipt of a message actor by a target actor, a complete history of a computation can be kept by recording these events. The facility to search through and examine such a history, combined with the facility to pre-set breakpoints or stopping points, and the ability to restore side effects, provides a powerful way to debug programs written in PLAMSA. The kinds of history-manipulation and breakpoint setting commands needed, and the ways they can be used, particularly on recursive programs without side effects, are presented.