13.3 Atoms: Their Types and Weights
13.3.3 Logical Links
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There is a host of link types embodying logical relationships as defined in the PLN logic system,
e.g.
e InheritanceLink e SubsetLink (aka ExtensionalInheritanceLink) e Intensional InheritanceLink
which embody different sorts of inheritance, e.g.
SubsetLink salmon fish IntensionalInheritanceLink whale fish InheritanceLink fish animal
and then
e SimilarityLink e ExtensionalSimilarityLink e IntensionalSimilarityLink
which are symmetrical versions, e.g.
SimilaritytLink shark barracuda IntensionalSimilarityLink shark dolphin ExtensionalSimiliarityLink American obese\_person
There are also higher-order versions of these links, both asymmetric
e ImplicationLink e ExtensionallmplicationLink e IntensionallmplicationLink
and symmetric
e EquivalenceLink e ExtensionalEquivalenceLink e IntensionalEquivalenceLink
These are used between predicates and links, e.g.
ImplicationLink EvaluationLink eat ListLink $X aan, EvaluationLink feel ListLink $X sick
or
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