ExtensionalSimilarityLink

A type of Link used in OpenCog to define extensional implication.

For more information, see this page

PLN Semantics

In PLN the ExtensionalSimilarityLink between 2 concepts is defined as ratio between the common properties (or elements) of two nodes and the total properties (or elements) of these nodes, i.e.,

$\operatorname {sim} (A,B)={\frac {P(A\wedge B)}{P(A\vee B)}}$$\operatorname {sim} (A,B)={\frac {P(A\wedge B)}{P(A\vee B)}}$

where $\wedge$$\wedge$ denotes the fuzzy intersection. The TV of the similarity of A and B can also be seen as the TV of concept $A\wedge B$$A\wedge B$ in the context $A\vee B$$A\vee B$ as explained in this thread [1]

See PredicateFormulaLink for an example of specifying formulas in Atomese.