Remembering Why to Remember:
Performance-Guided Case-Base Maintenance *

David B. Leake and David C. Wilson


Computer Science Department, Indiana University
Lindley Hall 215, Bloomington, IN 47405, U.S.A.
{leake , davwils}@cs.indiana.edu




Abstract. An important focus of recent CBR research is on how to
develop strategies for achieving compact, competent case-bases, as a
way to improve the performance of CBR systems. However, compactness 
and competence are not always good predictors of performance,
especially when problem distributions are non-uniform. Consequently,
this paper argues for developing methods that tie case-base maintenance
more directly to performance concerns. The paper begins by examining
the relationship between competence and performance, discussing the
goals and constraints that should guide addition and deletion of cases. It
next illustrates the importance of augmenting competence-hased criteria 
with quantitative performance-hased considerations, and proposes a
strategy for closely reflecting adaptation performance effects when compressing 
a case-base. It then presents empirical studies examining the
performance tradeoffs of current methods and the benefits of applying
fine-grained performance-based criteria to case-base compression, showing 
that performance-based methods may be especially important for
task domains with non-uniform problem distributions.


References
 Chomsky, N. 1965. Aspects of the Theory of Syntax. Cambridge, MA.: MIT
Press.
Doyle, M., and Cunningham, P. 1999. On balancing client-server load in intelligent 
web-based applications involving dialog. Technical Report TCD-CS-
1999-25, Trinity College Dublin.
Francis, A., and Ram, A. 1993. Computational models of the utility problem
and their application to a utility analysis of case-based reasoning. In In Proceedings 
of the Workshop on Knowledge Compilation and Speed- Up Learning.
Hart, P. E. 1968. The condensed nearest neighbor rule. IEEE Transactions on
Information Theory 14:515516.
Leake, D., and Wilson, D. 1998. Case-base maintenance: Dimensions and
directions. In Cunningham, P.; Smyth, B.; and Keane, M., eds., Proceedings
of the Fourth European Workshop on Case-Based Reasoning, 196207. Berlin:
Springer Verlag.
Leake, D., and Wilson, D. 1999. When experience is wrong: Examining CBR
for changing tasks and environments, In Proceedings of the Third International
Conference on Case-Based Reasoning, 218232. Berlin: Springer Verlag.
Portinale, L.; Torasso, P.; and Tavano, P. 1998. Proceedings of the thirteenth
european conference on artificial intelligence. In Dynamic Case Memory Management, 
7377. Chichester: Wiley.
Portinale, L.; Torasso, P.; and Tavano, P. 1999. Speed-up, quality, and competence 
in multi-modal reasoning. In Proceedings of the Third International
Conference on Case-Based Reasoning, 303--317. Berlin: Springer Verlag.
Smyth, B., and Cunningham, P. 1996. The utility problem analysed: A case-based 
reasoning perspective, In Proceedings of the Third European Workshop
on Case-Based Reasoning, 392399. Berlin: Springer Verlag.
Smyth, B., and Keane, M. 1995. Remembering to forget: A competence-preserving 
case deletion policy for case-based reasoning systems. In Proceedings
of the Thirteenth International Joint Conference on Artificial Intelligence, 377
382. Montreal: IJCAJ.
Smyth, B., and Keane, M. 1998. Adaptation-guided retrieval: Questioning the
similarity assumption in reasoning. Artificial Intelligence 102(2) :249293.
Smyth, B., and McKenna, E. 1999a. Building compact competent case-bases.
In Proceedings of the Third International Conference on Case-Based Reasoning.
Berlin: Springer Verlag.
Smyth, B., and McKenna, E. 1999b. Footprint-based retrieval, In Proceedings of
the Third International Conference on Case-Based Reasoning. Berlin: Springer
Verlag.
van Someren, M.; Surma, J.; and Torasso, P. 1997. A utility-based approach
to learning in a mixed case-based and model-based reasoning architecture. In
Proceedings of the Second International Conference on Case-Based Reasoning,
477-488. Berlin: Springer Verlag.
Zbu, J., and Yang, Q. 1999. Remembering to add: Competence-preserving
case-addition policies for case base maintenance, In Proceedings of the Fifteenth
International Joint Conference on Artificial Intelligence. Morgan Kaufmann.
