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

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Example 11.3: Prove that Ā(p) ≡ ¬S(¬p).<br />

Proof: Let at state s, Ā(p) be true.<br />

We write formally,<br />

s ╞ Ā (p) . (1)<br />

Let us suppose that<br />

s ╞ S (¬p). (2)<br />

Then there exists a state s’ , the next state of s such that<br />

s’╞ ¬p. (3)<br />

However, since s ╞ Ā(p) ,<br />

s’╞ p. (4)<br />

Consequently, the supposition that s ╞ S(¬p) is wrong, i.e. s |≠ S(¬p) ,<br />

Or, s ╞ ¬S(¬p),<br />

which yields<br />

Ā(p) ≡ ¬S( ¬p) . <br />

Example 11.4: Prove that Ā (pq) ( Ā(p) Ā(q)).<br />

Proof: Given that at state, say, s, Ā (pq),<br />

i.e., s ╞ Ā (pq) (1)<br />

also given s ╞ Ā(p)<br />

Let us assume that<br />

(2)<br />

s╞ ¬Ā(q) , (3)<br />

i.e., Ā(q) does not follow from state s.<br />

Further, as Ā(q) ≡ ¬S ¬q. (4)<br />

∴ ¬ Ā(q) = S ¬q. (5)<br />

Substituting (5) in (3) we have<br />

s ╞ S ¬q.<br />

If there exists a next state of s, say s’ , then

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