A TMS-based Approach for Efficient Conflict Resolution and Replanning in Resource Allocation Problems

ions are widely considered as very good techniques in order to reduce the search space and, consequently, to simplify the problem solving procedure. Abstraction is defined by Giunchiglia and Walsh (7) as the mapping of a problem representation into a simpler one that satisfies some desirable properties in order to reduce the complexity of reasoning. The problem is solved in a simplified abstract space and the solution is then mapped back to the more complex ground space. The main concepts of two temporal abstraction techniques, the value-assignment delay heuristic and summarization, are outlined with respect to the proposed problem solving formulation: (i) Value-Assignment Delay heuristic: A value-assignment delay (VAD) heuristic, primarily aimed at list-colouring problems, has been proposed by Choueiry and Faltings (5, 8). The main idea of the heuristic is to delay the assignment of the most solicited values and try to solve the simplified problem without them. The adopted approach lets the variables compete over other possible assignments and, finally, distributes the delayed values over those variables that really cannot do without them. The choice of values to be delayed is based on measurements of resource contention. The VAD heuristic implicitly causes a partitioning of objects by “grouping values on the trunk of the partitioning tree and by pushing variables into the leaves”. That is, when value contention takes place, it decomposes the resource allocation problem in a way that decision making upon resource assignments is performed primarily for the less competitive variables.