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prologuniversalexistential-typequantifiers

universal and existential quantifier in prolog

How can I implement following rules in prolog.

I write the “ No spiders are mammals” sentence as Existential and universal:

¬∃x(mammals(X) ∧ spider(X) ) //It is not the case that mammals are spider

∀X(mammals(X) ⇒ ¬spider(X)) //All mammals are non-spider.
Solution

  • Suppose you have a database with the following facts:

    mammals(cat).
mammals(dog).
 ...

spider(blackwidow).
 ...

    Now you can issue a rewrite your sentence into a prolog query quite straightforward:

    ¬∃x(mammals(X) ∧ spider(X) ) //It is not the case that mammals are spider

    ?- \+((mammals(X), spider(X))).
true.

    and

    ∀X(mammals(X) ⇒ ¬spider(X)) //All mammals are non-spider.

    ?- forall(mammals(X), \+spider(X)).
true.