The approximate reasoning capability of Milord II is based on a family of finitely-valued logics which are local to each module and defined as an algebra of truth-values. This allows the system to use a degree of truthness for the concepts involved in the system, then giving graduated results in function of the inherent uncertainty of the data and knowledge involved in the treatment of pneumonia.
The user-defined logic of a module is composed by the declarations of: 1) an ordered set of linguistics terms representing truthness degrees between true and false and, 2) a conjunction operator.
In Terap-IA we have used the same set of eight linguistic terms and the same connective modelling in all modules. The terms are the following: impossible, very few possible, few possible, slightly possible, possible, quite possible, very possible and definite, where impossible stands for the boolean false and definite for the boolean true.
Table 1 represents the conjunction operator used in Terap-IA, where the linguistic terms are abbreviated.
Table: Conjunction table for Terap-IA.
The many-valued logic of a module is completely determined as soon as the set of linguistic terms and the conjunction operator are chosen. So, varying these two features we may generate different multiple-valued logics. In Terap-IA we use the same logic for all modules.