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

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that the inferences will be minimally disturbed in the worst case. This is<br />

possible in the present context, if we can adjust threshold to a transition that<br />

lies on a reasoning path with the least fuzzy gain. Further, the selected<br />

transition should not induce limitcycles in the neighborhood cycles. An<br />

algorithm [8] for elimination of limitcycles can be easily constructed based on<br />

the last two criteria.<br />

23.5.6 Non-monotonic Reasoning in a FPN<br />

In this section, a new technique for non-monotonic reasoning, which<br />

eliminates one evidence out of each pair of contradictory evidences from<br />

an FPN, will be presented. However, before presenting the technique, the<br />

possible ways by which non-monotonicity is introduced into a FPN will be<br />

illustrated.<br />

Creeping of non-monotonicity into a FPN: Contradictory<br />

evidences may appear in a FPN because of i) inconsistency in a<br />

database, ii) inconsistency in production rules, <strong>and</strong> iii) uncertainty<br />

of <strong>info</strong>rmation in a database. To illustrate how contradictory evidences <strong>and</strong><br />

hence non-monotonicity are introduced into the FPN, we consider the<br />

following examples.<br />

i) Inconsistency in database: To illustrate how inconsistency in database<br />

finds its way in the FPN, let us consider a database that includes the<br />

<strong>info</strong>rmation, namely, has-alibi (ram), has-no-alibi (ram), has-precedenceof-murder<br />

(ram). Further assume that ‘ram’ is included in the list of<br />

suspects. The set of PRs before instantiation with the name of suspects <strong>and</strong><br />

the person murdered are listed below:<br />

PR1: not-suspect (X) :- has-precedence-of-murder (X),<br />

Has-alibi (X).<br />

PR2: culprit (X) :- has-precedence-of-murder (X),<br />

has-no-alibi (X).<br />

Now, first by instantiating the variable X in the above rules by ‘ram’<br />

<strong>and</strong> then checking the antecedent clauses of the resulting rules in the<br />

database, we finally form the FPN, shown in fig. 23.9. In this fig. d1, d2, d3,<br />

d4 <strong>and</strong> d5 represent has-alibi(ram), has-precedence-of-murder (ram), has-noalibi(ram),<br />

not-suspect (ram) <strong>and</strong> culprit (ram ) respectively. Thus the<br />

contradictory evidences has-alibi (ram) <strong>and</strong> has-no-alibi (ram) could enter<br />

into the FPN because of inconsistency in the database.

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