A fuzzy logic approach to the management of linguistically expressed uncertainty

A description is given to the expert system shell called MILORD and, in particular, its management of uncertainty. This shell contains two inference engines, a rule-oriented editor, a rule compiler, and an explanation module. MILORD can be used to perform three different calculi of uncertainty, on an expert-defined set of linguistic labels, depending on three different models of the conjunction, disjunction, and implication operators. The internal representation of each linguistic label is a possibility distribution on the unit interval. The calculus performed on these labels is not closed in general, and, therefore, it is necessary to close it by means of a linguistic approximation process. This, in turn, allows the conjunction, disjunction, and implication operations to be precomputed for all the pairs of linguistic labels, sorting the results in matrices. Thus, when MILORD is run on a knowledge base, the propagation and combination of uncertainty is performed accessing the precomputed matrices. The examples given correspond to an application to the diagnosis of pneumonias.<>