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

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here, for instance, the THEN part of each rule has to be encoded by some<br />

pieces of knowledge. Ohm’s law, for example, can be formalized as follows:<br />

IF V= (voltage across a component) &<br />

Z= (impedance of the component) &<br />

I= (current through the component)<br />

THEN V:= I * Z.<br />

Kirchoff’s voltage law (KVL) in a loop can be represented as follows:<br />

IF (no. of circuit component in a loop = n) &<br />

(voltage across <strong>and</strong> current through Z1 are V1 <strong>and</strong> I1 ) &<br />

(voltage across <strong>and</strong> current through Z2 are V2 <strong>and</strong> I2) &<br />

. .<br />

. .<br />

(voltage across <strong>and</strong> current through Zn are Vn <strong>and</strong> In) &<br />

(total driving emf in a loop = V)<br />

THEN ( V = V1 + V2 + …….+ Vn ) OR<br />

(V = I1 * Z1 + I2 * Z2 + …+ In*Zn).<br />

After the construction of the knowledge base, the performance of the<br />

system in fig. 21.1 is evaluated through verification <strong>and</strong> validation of the<br />

system. A question that then naturally arises is how to compare the<br />

performance of the proposed system with an ‘ideal’ one. One way to solve the<br />

problem is to call the expert, based on whose knowledge the system is built.<br />

Suppose the expert selects superposition theorem to solve a problem but the<br />

expert system built with his expertise cannot identify ‘superposition’ theorem<br />

as the best choice for solving the problem. Obviously, there is a problem with<br />

the system design. Most likely there exist some loopholes in the identification<br />

of problem characteristics. So, reformulation of the problem characteristics<br />

through validation of the system could overcome this problem. In case<br />

reformulation of the new problem characteristics cannot be inferred by the<br />

validation procedure, then the structures used to represent concepts or the<br />

knowledge base could be re-designed. This is done by invoking a verification<br />

procedure.<br />

Apart from validation <strong>and</strong> verification, another significant issue in<br />

improving the performance of an expert system lies with its maintenance. The<br />

knowledge base of an expert system is gradually enriched with new pieces of<br />

knowledge. Unless there is some formalization of entering new rules,<br />

inconsistencies in various forms may creep into the system. Further, there<br />

must be some sort of partitioning in the knowledge base; otherwise, the<br />

system will suffer from inefficient pattern matching cycle.

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