His work on planning focused on the "classical" case rather than on hierarchical task network planning. In 1990 he was named a Fellow of the Association for the Advancement of Artificial Intelligence, one of the first group of Fellows. In 1996 he (and Hector Geffner and Blai Bonet independently) discovered "estimated-regression planning", based on the idea of heuristic search with an estimator derived from a simplified domain model by reasoning backward ("regression") from the goal.
His work on planning centered on the "traditional" approach rather than hierarchical task network planning. In 1990 he was designated a Fellow of the Association for the Advancement of Artificial Intelligence, one of the first group of Fellows. In 1996 he (and Hector Geffner and Blai Bonet independently) discovered "estimated-regression planning", based on the idea of heuristic search with an estimator derived from a simplified domain model by reasoning backward ("regression") from the goal.