Case Based Reasoning (CBR) vs Rule Based Reasoning (RBR)

Sunday, December 23, 2007 | Labels: , | |

Rule Based Reaoning (RBR) requires us to elicit an explicit model of the domain. As we all know and have experienced, knowledge acquisition has a set of associated problems. In contrast, Case Based Reasoning (CBR) does not require an explicit model. Cases that identify the significant features are gathered and added to the case base during development and after deployment. This is easier than creating an explicit model, as it is possible to develop case bases without passing through the knowledge-acquisition bottleneck.

Domain experts would have accumulated knowledge over the years through experience. It would be a blunder mistake if we do not use them to our advantage. But the difficulty lies in getting the experts to list down the decision rules which they use. It is a Herculean task to comprehensively recall all the tacit rules which they have come to adopt. However, they usually have little difficulty in recalling concrete cases, which they have encountered in practice. Thus, their mental set appears to be oriented towards a Case Based Reasoning approach.

Developing a CBR system is much faster and easier than constructing a rule-based equivalent. Case bases do not have to be complete when they are deployed for use, as even non-computer experts can add cases to the existing structure.

Maintenance with a Rule Based System may be a nightmare. If the rules are not written clearly, it would lead to many sleepless nights of debugging. Maintenance with Case Based Systems are much easier and straightforward.

When rules are added or deleted from a rule-based system, the system has to be checked for conflicting rules and redundant rules. An addition or deletion of a case from the case base does not any further checking or debugging. But it have to be noted that while it does not affect the system’s functioning, it may have an impact on the outcome of the system.


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