The GERRY scheduling and rescheduling system being applied to coordinate Space Shuttle ground processing is described. The system uses constraint-based iterative repair, a technique that starts with a complete but possibly flawed schedule and iteratively improves it by using constraint knowledge within repair heuristics. The tradeoff between the informedness and the computational cost of several repair heuristics is explored. It is shown empirically that some knowledge can greatly improve the convergence speed of a repair-based system, but that too much knowledge can overwhelm a system and result in degraded performance.
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