On the implementation and evaluation of ABTWEAK

In this paper, we describe the implementation and evaluation of the ABTWEAK planning system, a test bed for studying and teaching concepts in partial-order planning, abstraction, and search control. We start by extending the hierarchical, precondition-elimination abstraction of ABSTRIPS to partial-order-based, least-commitment planners such as TWEAK. The resulting system, ABTWEAK, illustrates the advantages of using abstraction to improve the efficiency of search. We show that by protecting a subset of abstract conditions achieved so far, and by imposing a bias on search toward deeper levels in a hierarchy, planning efficiency can be greatly improved. Finally, we relate ABTWEAK to other planning systems SNLP, ALPINE, aad SIPE by exploring their similarities and differences.