Using Guidelines to Constrain
Interactive Case-Based HTN Planning

Hctor Muoz-Avila+, Daniel C. McFarlane, David W. Aha,
Len Breslow, James A. Ballas, & Dana S. Nau+

+ Department of Computer Science
University of Maryland
College Park, MD 20742-3255
lastname@cs.umd.edu
(301) 405-2684 | FAX: 405-6707
 Navy Center for Applied Research in AI
Naval Research Laboratory
Washington, DC 20375
lastname@aic.nrl.navy.mil
(202) 404-4940 | FAX: 767-3172



Abstract. This paper describes HICAP, a general-purpose, interactive
case-based plan authoring architecture that can be applied to decision
support tasks to yield a hierarchical course of action. It integrates a hierarchical 
task editor with a conversational case-based planner. HICAP
maintains both a task hierarchy representing guidelines that constrain
the final plan and the hierarchical social organization responsible for
these tasks. It also supports bookkeeping, which is crucial for real-world
large-scale planning tasks. By selecting tasks corresponding to the hierarchys 
leaf nodes, users can activate the conversational case-based planner
to interactively refine guideline tasks into a concrete plan. Thus, HICAP
can be used to generate context sensitive plans and should be useful for
assisting with planning complex tasks such as noncombatant evacuation
operations. We describe an experiment with a highly detailed military
simulator to investigate this claim. The results show that plans generated
by HICAP were superior to those generated by alternative approaches.
References

Aha, D. W., & Breslow, L. A. (1997). Refining conversational case libraries.
Proceedings of the Second International Conference on CBR (pp. 267278).
Providence, RI: Springer.
Bergmann, R., Muoz-Avila, H., Veloso, M., Melis, E. (1998). Case-based reasoning 
applied to planning tasks. In M. Lenz, B. Bartsch-Spoerl, H.-D.
Burkhard, & S. Wess (Eds.) CBR Technology: From Foundations to Applications. 
Berlin: Springer.
Bergmann, R. & Wilke, W. (1995). Building and refining abstract planning
cases by change of representation language. Journal of AI Research, 3, 53
118.
Branting, L. K., & Aha, D. W. (1995). Stratified case-based reasoning: Reusing
hierarchical problem solving episodes. Proceedings of the Fourteenth International 
Joint Conference on Al (pp. 384390). Montreal, Canada: Morgan
Kaufmann.
Breslow, L., & Aha, D. W. (1997). NaCoDAE: Navy Conversational Decision
Aids Environment (TR AIC-97-018). Washington, DC: Naval Research Laboratory, 
Navy Center for Applied Research in Artificial Intelligence.
Carrick, C., Yang, Q., Abi-Zeid, I., & Lamontagne, L. (1999). Activating CBR
systems through autonomous information gathering. To appear in Proceedings 
of the Third International Conference on Case-Based Reasoning. Munich, 
Germany: Springer.
Ceranowicz, A. (1994). Modular Semi-Automated Forces. Proceedings of the
Winter Simulation Conference of the ACM (pp. 755761). New York, NY:
IEEE.
DoD (1994). Joint tactics, techniques and procedures for noncombat evacuation
operations (Joint Report 3-07.51, Second Draft). Washington, DC: Department of Defense.
Erol, K., Nau, D., & Hendler, J. (1994). HTN planning: Complexity and expressivity. 
Proceedings of the Twelfth National Conference on Artificial Intelligence 
(pp. 11231128). Seattle, WA: AAAI Press.
Fikes, R.E., & Nilsson, N.J. (1971). Strips: A new approach to the application
of theorem proving in problem solving. Artificial Intelligence, 2,189208.
Kambhampati, S. (1994). Exploiting causal structure to control retrieval and
refitting during plan reuse. Computational Intelligence, 10, 213244.
Lambert, Kirk S. (1992). Noncombatant evacuation operations: Plan now or
pay later (Technical Report). Newport, RI: Naval War College.
Mitchell, S.W. (1997). A hybrid architecture for real-time mixed-initiative planning 
and control. Proceedings of the Ninth Conference on Innovative Applications 
of AI (pp. 10321037). Providence, RI: AAAI Press.
Muoz-Avila, H., Breslow, L.A., Aha, D.W., & Nau, D. (1998). Description and
functionality of HTE (TR AIC-98-022). Washington, DC: NRL, NCARAI.
Muoz-Avila, H., Aha, D.W., Breslow, L. & Nau, D. (1999). HICAP: An interactive 
case-based planning architecture and its application to noncombatant
evacuation operations. To appear in Proceedings of the Ninth National Conference 
on Innovative Applications of Artificial Intelligence. Orlando, FL:
AAAI Press.
Nau, D. S., Cao, Y., Lotem, A., & Muoz-Avila, H. (1999). SHOP: Simple
Hierarchical Ordered Planner. To appear in Proceedings of the Sixteenth
National Conference on Artificial Intelligence. Stockholm, Sweden: Morgan
Kaufmann.
Racine, K., & Yang, Q. (1997). Maintaining unstructured case bases. Proceedings 
of the Second International Conference on CBR (pp. 553564). Providence, RI: Springer.
Sachtleben, G.R. (1991). Operation Sharp Edge: The Corps MEU (SOC) program 
in action. Marine Corps Gazette, 11, 7686.
Siegel, A.B. (1991). Eastern Exit: The noncombatant evacuation operation
(NEO) from Mogadishu, Somalia, in January 1991 (TR CRM 91-221). Arlington, 
VA: Center for Naval Analyses.
Siegel, A.B. (1995). Requirements for humanitarian assistance and peace operations: 
Insights from seven case studies (TR CRM 94-74). Arlington, VA:
CNA.
Veloso, M., Mulvehill, A.M., & Cox, M.T. (1997). Rationale-supported mixed-initiative 
case-based planning. Proceedings of the Ninth Conference on Innovative
 Applications of Artificial Intelligence (pp. 10721077). Providence,
RI: AAAI Press.
Wilkins, D.E. (1998). Using the SIPE-2 planning system: A manualfor Version
5.0 (Working Document). Menlo Park, CA: Stanford Research International,
Artificial Intelligence Center.
