Abstract
The inference strategies represent the logical nuclei of expert systems. Those pure
mathematical approach makes difficult the access of practitioners involved in the design and use
of expert systems, at the interpretation and deciphering of the inference mechanisms. The present
paper, dedicated first of all to the practitioners, has as objective the presentation of some easy and
engineering techniques of approach, based upon means that are easy to interpret such as the
qualitative inference table and the analysis in the state space. The introduced notions are sampled
on a segment of an existing expert system, designed for the diagnosis of the isolated paralysis of
extraocular muscles. The segment is reported on the gone over at the design of the mentioned
expert system by the identification of facts and rules and at the build of the logical model
associated to the examination based on the inference strategy "forward chaining".
