Wilkins, D. E. (1985). Hierarchical planning: Definition and implementation. SRI INTERNATIONAL MENLO PARK CA ARTIFICIAL INTELLIGENCE CENTER.
There is considerable ambiguity involved in hierarchical planning. We present a definition of the latter, and examine several of the reasons for this confusion. An explication of hierarchical planning implementations entails two distinct notions: abstraction level and planning level. A problem and currently implemented planners that is causing by mixing these two levels is presented in various remedies suggested. Two solutions that have been implemented in the current SIPE planning system are described.