SHOP2: An HTN Planning System, Dana S. Nau, T. C. Au, O. Ilghami, U. Kuter, J. W. Murdock, D. Wu, F. Yaman, 2003Journal of Artificial Intelligence Research, Vol. 20 (AI Access Foundation)DOI: 10.1613/jair.1368 - This paper describes SHOP2, a well-known Hierarchical Task Network (HTN) planning system, offering insights into classical hierarchical planning methods and their implementation.