Another Look at Frames

The success of MYCIN-like systems has demonstrated that for many diagnostic tasks expert behavior can be successfully captured in simple goaldirected production systems. However, even for this class of problems, difficulties have arisen with both the representation and control mechanisms. One such system, PUFF (Kunz et al., 1978), has established a creditable record in the domain of pulmonary function diagnosis. The representation problems in PUFF are manifest in a number of rules that have awkward premises and conclusions. The control problems are somewhat more severe. Physicians have criticized PUFF on the grounds that it asks questions that do not follow a logical line of reasoning and that it does not notice data that are atypical or erroneous for the determined diagnosis. In the CENTAUR sygtem, described in Chapter 23, an attempt was made to correct representational deficiencies by using prototypes (frames) to characterize some of the system's knowledge.