Temporal Knowledge Representation and Reasoning for Project Planning
Final rept. 1 Feb 1987-31 Jan 1988
IOWA UNIV IOWA CITY DEPT OF MANAGEMENT SCIENCES
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The author has written a working computer program which allows a user or a different module of an AI planning program to specify a set of temporal constraints including disjunctive constraints. In the context of a point-based temporal model, my program has required several innovative design choices. The program will find a feasible solution to the constraints if one exists, otherwise it will identify a contradiction. It is especially appropriate when adding new constraints to currently satisfiable existing constraints. The philosophical approach of dependency-directed backtracking is employed. This is implemented in a way that takes account of my problems special structure. The program is particularly successful in certain examples for which chronological backtracking would be hopelessly inefficient. Other notorious examples require time-consuming search. These examples reveal important tradeoffs between explicitly storing temporal knowledge and deriving appropriate temporal knowledge on demand. Particular instances have been identified where explicit storage is critical for avoiding expensive search. Keywords Knowledge based systems.
- Computer Programming and Software