Rules

head <- body. derives new knowledge: whenever the body holds, the head holds. Body conditions are joined with AND; OR alternatives must be explicitly grouped. Rules are written recursively rather than as listed closures.

// From a taxonomy fact to a derived membership.
?X:Mortal <- ?X:Human.

// A derivation over two references.
?X[hasUncle -> ?U] <- ?X[hasParent -> ?P] AND ?P[hasBrother -> ?U].

// Recursive closure: one step plus the transitive step.
?D[requires -> ?R] <- ?D[needs -> ?M] AND ?M[requires -> ?R].