Negation as failure
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| - | An '''argument from ignorance''', also known as '''argumentum ad ignorantiam''' or "appeal to ignorance" (where "ignorance" stands for: "lack of evidence to the contrary"), is an [[inference]] that a proposition P is false from the fact that P is not proved to be true or known to be true. | + | '''Negation as failure''' ('''NAF''', for short) is a [[non-monotonic logic|non-monotonic]] inference rule in [[logic programming]], used to derive <math>\mathrm{not}~p</math> (i.e. that <math>~p</math> is assumed not to hold) from failure to derive <math>~p</math>. Note that <math>\mathrm{not} ~p</math> can be different from the statement <math>\neg p</math> of the [[negation|logical negation]] of <math>~p</math>, depending on the completeness of the inference algorithm and thus also on the formal logic system. |
| - | ==See also== | + | Negation as failure has been an important feature of logic programming since the earliest days of both [[Planner (programming_language)|Planner]] and [[Prolog]]. In Prolog, it is usually implemented using Prolog's extralogical constructs. |
| - | * [[Argument from silence]] | + | |
| - | * [[False dilemma]] | + | |
| - | * [[Negation as failure]] | + | |
| - | * [[Philosophic burden of proof]] | + | |
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Negation as failure (NAF, for short) is a non-monotonic inference rule in logic programming, used to derive <math>\mathrm{not}~p</math> (i.e. that <math>~p</math> is assumed not to hold) from failure to derive <math>~p</math>. Note that <math>\mathrm{not} ~p</math> can be different from the statement <math>\neg p</math> of the logical negation of <math>~p</math>, depending on the completeness of the inference algorithm and thus also on the formal logic system.
Negation as failure has been an important feature of logic programming since the earliest days of both Planner and Prolog. In Prolog, it is usually implemented using Prolog's extralogical constructs.
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