CALCULATING CRITICALITIES

We present a novel method for building ABSTRIPS style abstraction hier archies in planning. The aim of this method is to minimize search by l imiting backtracking both between abstraction levels and within an abs traction level. Previous approaches for building ABSTRIPS style abstra ctions have determined the criticality of operator preconditions by re asoning about plans directly. Here, we adopt a simpler and faster appr oach where we use numerical simulation of the planning process, We dev elop a simple but powerful theory to demonstrate the theoretical advan tages of our approach, We use this theory to identify some simple prop erties lacking in previous approaches but possessed by our method, We demonstrate the empirical advantages of our approach by a set of four benchmark experiments using the ABTWEAK system, We compare the quality of the abstraction hierarchies generated with those built by tie ALPI NE and HIGHPOINT algorithms.