A History Keeping Debugging System for PLASMA

Unknown author (1977-05)

Artificial Intelligence Laboratory Massachusetts Institute of Technology Working papers are informal papers intended for internal use. This report describes research conducted at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for this research was provided by the Office of Naval Research under contract N00014-75-C-0522.

Working Paper

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.