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

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the connectionist approach will replace the classical approach in all respects.<br />

This, however, is a too optimistic proposition, as the current ANNs require<br />

significant evolution to cope with the problems involved in logic<br />

programming <strong>and</strong> non-monotonic reasoning. The symbolic <strong>and</strong> connectionist<br />

approach, therefore, will continue co-existing in intelligent machines until the<br />

latter, if ever, could replace the former in the coming years.<br />

1.6.2 Non-Deterministic Computation<br />

The AI problems are usually solved by state-space approach, introduced in<br />

section 1.3. This approach calls for designing algorithms for reaching one or<br />

more goal states from the selected initial state(s). The transition from one<br />

state to the next state is carried out by applying appropriate rules, selected<br />

from the given knowledge base. In many circumstances, more than one rule is<br />

applicable to a given state for yielding different next states. This <strong>info</strong>rmally is<br />

referred to as non-determinism. Contrary to the case, when only one rule is<br />

applicable to a given state, this system is called deterministic. Generally AI<br />

problems are non-deterministic. The issues of determinism <strong>and</strong> nondeterminism<br />

are explained here with respect to an illustrative knowledge-based<br />

system. For instance, consider a knowledge base consisting of the following<br />

production rules <strong>and</strong> database.<br />

Production Rules<br />

PR1: IF (A) AND (B) THEN ( C ).<br />

PR2: IF ( C ) THEN ( D).<br />

PR3: IF ( C ) AND ( E ) THEN (Y).<br />

PR4: IF (Y) THEN (Z).<br />

Database: A, B, E.<br />

The graph representing the transition of states for the above reasoning<br />

problem is presented in fig.1.12. Let A <strong>and</strong> B be starting states <strong>and</strong> Z be the<br />

goal state. It may be noted that both PR2 <strong>and</strong> PR3 are applicable at state (C)<br />

yielding new states. However, the application of PR3 at state (C) can<br />

subsequently lead to the goal state Z, which unfortunately remains unknown<br />

until PR4 is applied at state Y. This system is a typical example of nondeterminism.<br />

The dropping of PR2 from the knowledge base, however, makes<br />

the system deterministic. One formal approach for testing determinism / nondeterminism<br />

of a reasoning system can be carried out by the following<br />

principle:

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