Methodological approach to the construction of expert knowledge base

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The main features of our approach to the construction of expert knowledge base for the diagnostics of acute medicinal poisoning  are the following:

1. 19 knowledge bases imitating an expert diagnostics skill are constructed successively for

different classes of poisoning.

2. For given class an expert defines the subset of diagnostic signs and its values needed for the

diagnostics. All combinations of the diagnostic sign values create the space of possible patient images.

3. An expert is asked to order values of each diagnostic sign by typicality par respect to given

class of intoxication.

4. The expert’s knowledge is elicited by the presentation on computer screen the description of

different CS in the terms of diagnostic sign values. An expert is to give its classification into three

classes: strong intoxication by a drug from the corresponding class; intoxication by such drug; no

intoxication by a drug from the corresponding class (different cause of intoxication).

5. To save expert efforts the utilization of binary relation of domination by typicality is done.

If an expert allocates one CS to the class of intoxication, some others CS having all diagnostic signs values (from the subset used) not less typical for this class and at least one value-more typical, also belong to the class. Using such binary relation it is possible to classify several CS on the basis of one expert decision. In other words a cone of dominance by typicality is constructed in the space of diagnostic signs.

6. Fortunately such cones are intersecting ones. It creates the possibility for checking an expert

information for the absence of contradictions and for finding the special cases of diagnostic signs

dependence. For each contradictory case the corresponding information is presented on computer

screen to an expert for the detail analysis.

7. The special algorithm is used for the choice of the next CS presented to an expert for the

classification on the base of the criteria of minimum number of questions needed for the classification of all CS belonging to given class.

8. For the classes of medicinal poisoning described by similar diagnostics signs the special

knowledge bases for differential diagnostics are constructed.

New approach in the problems of knowledge elicitation have been tested previously on different practical tasks [3,4].

There is the group of methods based on the approach [4,5]. More advanced of them allow to receive from an expert the classification of 700-800 CS per hour [5].

After construction, the knowledge bases were tested by the presentation of different difficult cases to the computer and to the expert. The results demonstrated the close imitation of expert reasoning.

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