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The ability to backtrack, or retrace, the execution of a computer program has gained wider acceptance recently as a desired feature within a programming language. This is particularly useful in two different applications: (1) In debugging systems where the trace output is saved and can be interrogated under programmer control 1, 3; (2) In artificial intelligence applications where one is trying to prove a certain result. It is frequently necessary to backup the proof and try some alternative path 2.
Marvin V. Zelkowitz (Sat,) studied this question.