The paper is organized as follows. Section 2 shows the complexity of the pattern classification domain. Section 3 poses the problem of classifier design in terms of a general design task. Section 4 describes the CommonKADS model for classifier design. Section 5 deals with the implementation details. Section 6 describes the application of the expert system to Alzheimer’s diagnosis. Section 7 presents the results of the evaluation of the expert system on different well-known datasets.