The confidence of rule {X → c} is denoted as θ(X − → c), and is the conditional probability of c given the termset X , that is, θ(X − → c) = σ(X ∪c) σ(X ) .
in this context, a classifier is denoted as R, and it is composed of a set of rules {X − → c} extracted from D. R is represented as a pool of entries with the form <key, properties>, where key={X , c} and properties={σ(X ), σ(X ∪ c), θ(X → c)}.