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Artificial Intelligence and Soft Computing: Behavioral ... - Arteimi.info

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finer level of difference in their usage, are being used interchangeably in the<br />

existing literature of expert systems. Strictly speaking, ‘validation’ refers to<br />

‘building the right system’ [3]-[4] that truly resembles the system intended to<br />

be built. In other words, validation corresponds to testing the performance of<br />

the system, <strong>and</strong> suggests reformulation of the problem characteristics <strong>and</strong><br />

concepts based on the deviation of its performance from that of the ideal<br />

system. The ‘ideal system’, in general, could be the expert himself or an<br />

already validated system.<br />

‘Verification’, on the other h<strong>and</strong>, deals with implementational issues. For<br />

instance, it includes redesigning the organization of the knowledge base <strong>and</strong><br />

refinement of the pieces of knowledge so that the performance of the expert<br />

system is comparable to that of an ideal system.<br />

Buchanan [8] first proposed the life cycle of expert systems with regard<br />

to the various stages of their development. For illustrating the scope of the<br />

validation <strong>and</strong> verification schemes in an expert system, we slightly extend<br />

this model (vide 21.1). In this figure, the first four major steps are<br />

involve d to represent the problem by an equivalent knowledge base, <strong>and</strong> the<br />

remaining two steps are employed to improve the performance of the system<br />

through feedback cycles. To illustrate the figure, let us consider the domain of<br />

‘circuit problems’. An electrical circuit consists of components like resistors,<br />

inductors, capacitors, transistors <strong>and</strong> electrical conductors (wire).<br />

Problems of common<br />

domain<br />

Problems<br />

Characteristics<br />

identification<br />

Finding concepts to<br />

represent problems<br />

Reformulate problem<br />

characteristics<br />

Designing structures<br />

to represent concepts<br />

Verify knowledge base<br />

Represent<br />

knowledge for each<br />

structures<br />

Redesign structures Redesign<br />

knowledge<br />

Fig. 21.1: Life cycle of an expert system.<br />

Validate knowledge

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