A type of Link used to describe intensional similarity between concepts.

## PLN Semantics

In PLN the IntensionalSimilarityLink between 2 concepts corresponds to the extensional similarity of their patterns (supersets, accounting for their simplicity). Formally

IntensionalSimilarityLink <TV>
A
B


is equivalent to

 ExtensionalSimilarityLink <TV>
$Z EvaluationLink GroundedPredicateNode "pattern-of" ListLink$Z
X
$Z EvaluationLink GroundedPredicateNode "pattern-of" ListLink$Z
Y


where the pattern-of predicate is a GroundedPredicateNode defined so that

$\displaystyle \operatorname{pattern-of}(Z,X) = s(Z) \times (P(Z|X) - P(Z|\neg X))^+$

where s(Z) is the prior of Z, reflecting it's simplicity, that is the simpler Z and the stronger it's discriminating power over X, the more it is a pattern of X. For the discriminating power of Z over X we also say that X is attracted to Z, that we can represent with the following link

 AttractionLink
X
Z


where the strength of the TV of such attraction link is $\displaystyle (P(Z|X) - P(Z|\neg X))^+$ . Note that $\displaystyle (x)^+$ is the positive part of $\displaystyle x$ .

See PredicateFormulaLink for an example of specifying formulas in Atomese.