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Mark Drummond

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4 papers
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4

AAAI Conference 1994 Conference Paper

Just-In-Case Scheduling

  • Mark Drummond

This paper presents an algorithm, called Just- In-Case Schedulkg, for building robust schedules that tend not to break. The algorithm implements the common sense idea of being prepared for likely errors, just in case they should occur. The Just-In-Case algorithm analyzes a given nominal schedule, determines the most likely break, and reinvokes a scheduler to generate a contingent schedule to cover that break. After a number of iterations, the Just-In-Case algorithm produces a “multiply contingent” schedule that is more robust than the original nominal schedule. The algorithm has been developed for a real telescope scheduling domain in order to proactively manage schedule breaks that are due to an inherent uncertainty in observation durations. The paper presents empirical results showing that the algorithm performs extremely well on a representative problem from this domain.

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AAAI Conference 1990 Conference Paper

Anytime Synthetic Projection: Maximizing the Probability of Goal Satisfaction

  • Mark Drummond

This paper presents a projection algorithm for incremental control rule synthesis. The algorithm synthesizes an initial set of goal-achieving control rules using a combination of situation probability and estimated remaining work as a search heuristic. This set of control rules has a certain probability of satisfying the given goal. The probability is incrementally increased by synthesizing additional control rules to handle “error” situations the execution system is likely to encounter when following the initial control rules. By using situation probabilities the algorithm achieves a computationally effective balance between the limited robustness of triangle tables and the absolute robustness of universal plans.

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IJCAI Conference 1989 Conference Paper

Coal Ordering in Partially Ordered Plans

  • Mark Drummond
  • Ken Carrie

Partially ordered plans have not solved the goal ordering problem. Consider: a goal in a par­ tially ordered plan is an operator precondition that is not yet achieved; operators, orderings and variable bindings are introduced to achieve such goals. While the planning community has known how to achieve individual goals for some time, there has been little work on the prob­ lem of which one of the many possible goals the planner should achieve next. This paper argues that partially ordered plans do not use­ fully address the goal-ordering problem and then presents a heuristic called temporal coherence which does. Temporal coherence is an ad­ missible heuristic which provides goal-ordering guidance. Temporal coherence is admissible in the sense that if a solution exists in the plan­ ner's search space, then there will be a series of goal achievements permitted by the heuristic which can produce this solution.

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