PANDA, a system designed for hybrid planning, an extension of HTN planning developed at Ulm University, Germany. HTNPlan-P, preference-based HTN planning. HTN planning is strictly more expressive than STRIPS, to the point of being undecidable in the general case. However, many syntactic restrictions of HTN planning are decidable, with known complexities ranging from NP-complete to 2-EXPSPACE-complete, and some HTN problems can be efficiently compiled into PDDL, a STRIPS-like language. See also STRIPS Hierarchical control system - a feedback control system well suited for HTN planning References Automated planning and scheduling