Details of the Revised Therapy Algorithm

A program that is designed to provide sophisticated expert advice must cope with the needs of naive users who may find the advice puzzling or difficult to accept. This chapter describes additions to MYCIN that provide for explanations of its therapy decisions, the lack of which was a shortcoming of the original therapy recommendation code described in Section 5.4 of Chapter 5. It deals with an optimization problem that seeks to provide "coverage" for organisms while minimizing the number of drugs prescribed. There are many factors to consider, such as prior therapies and drug sensitivities, and a person often finds it hard to juggle all of the constraints at once. When the optimal solution is provided by a computer program, its correctness may not be immediately obvious to the user. This motivates our desire to provide an explanation capability to justify the program's results. The explanation capability derives from two basic programming considerations.