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

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5.2 Formal Definitions<br />

The following definitions, which will be referred to occasionally in the rest of<br />

the book, are in order.<br />

Definition 5.1: A connective is a logical operator that connects simple<br />

statements for constructing more complex statements.<br />

The list of connectives in propositional logic <strong>and</strong> their meaning is tabulated<br />

below.<br />

Table 5.1: Connectives in propositional logic<br />

Operators Notations<br />

AND Λ<br />

OR V<br />

Negation ¬ , ~<br />

If p then q p → q<br />

If p then q <strong>and</strong><br />

if q then p p ↔ q<br />

Implication ⇒<br />

Bi-directional<br />

Implication (IFF) ⇔<br />

Identity ≡<br />

Logical entailment |=<br />

Derivability |−<br />

It should be noted that AND <strong>and</strong> OR operators are sometimes<br />

referred to as conjunction <strong>and</strong> disjunction respectively. It may further be<br />

added that the provability <strong>and</strong> implication symbols have been used in an<br />

interchangeable manner in this book. The author, however, has a strong<br />

reservation to use implication symbol in place of if-then operator <strong>and</strong> vice<br />

versa [3]. The symbol “x |− y ” implies that y has been derived from x by<br />

following a proof procedure. The logical entailment relation: “x |= y ” on<br />

the other h<strong>and</strong> means that y logically follows from x.

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