The calcium-phosphorus metabolism expert system module: a program developed in the ALEX Smalltalk/V shell

The object-oriented computing model of Smalltalk/V proved to be very well suited for the creation of a medical expert system on the diagnosis of calcium-phosphorus metabolism abnormalities. A major reason for this was that a disease could be viewed as a self-contained, active, entity. The expert system is implemented in ALEX, an expert system shell that is written in Smalltalk/V. The shell consists of classes and methods that can be modified, as needed, by the developer. The expert system is, at present, 140,000 bytes in size, and includes 43 diseases, arranged in 7 contexts. Sixty case reports were used to test the expert system. In 30 cases, there was complete agreement between clinician and expert system; in 12 cases, the expert system responded appropriately when presented with diseases that were not known to the system; and in 18 cases, the system gave plausible results.