A DIGITALIS THERAPY ADVISOR WITH EXPLANATIONS

• Authors: W. R. Swartout
• Venue: A DIGITALIS THERAPY ADVISOR WITH EXPLANATIONS
• Year: 1977

This thesis describes the English explanation facility of the OWL Digitalis Advisor, a program designed to advise physicians regarding digitalis therapy. The program is written in OWL, an English-based computer language being developed at MIT. The system can explain, in English, both the methods it uses and how those methods were applied during a particular session. In addition, the program can explain how it acquires information and tell the user how it deals with that information either in general or during a particular session. Most explanations are produced directly from the code used in prescribing digitalis and from information which is generated by the OWL interpreter as it runs. The ability of the program to translate its internal structure to an English explanation is provided by structuring the program using Semantic Model Programming. Each OWL procedure attempts to represent a single concept or idea that should be meaningful to the physician using the system. By organizing the program in this way, the explanations produced by the system tend to relate well to ideas with which the physician is already acquainted. In many current systems which ask the user a series of questions, a problem occurs if the user wishes to change his answer to a previous question. These systems accept the change, but must recompute all the results computed subsequent to that question to insure that none of them are affected. Clearly, this may involve a considerable amount of unnecessary recomputation. By using OWL, we obtain the data structures necessary to avoid this problem. An algorithm is described that allows the system to accept a changed answer without recomputing all prior results. This process is called updating. The updating algorithm presented here also allows the system to provide concise explanations of the effects of the changed answer.