Case-based reasoning is the process of solving new problems based on the solutions of previous problems. An auto mechanic, who fixes an engine by remembering that another car had the same symptoms, is using case-based reasoning. A lawyer who appeals to legal precedents to defend a case is using case-based reasoning. Also an engineer when copying elements of nature, is trying to treat it as "database solutions."
CBR also is an approach to incremental, sustained learning, since a new experience is retained each time a problem has been solved, making it immediately available for future problems. The CBR field has grown rapidly over the last few years, as seen by its increased share of papers at major conferences, available commercial tools, and successful applications in daily use.
The experiences (solution part) of the most similar case is then reused to solve the new problem presented to the system.
The processes involved in CBR have been described as a cyclical process comprising the four REs:
A new problem is matched against cases in the case base and one or more similar cases are retrieved. A solution suggested by the matching cases is then reused and tested for success. Unless the retrieved case is a close match the solution will probably have to be revised producing a new case that can be retained.