 Inference on knowledge: Where \(M = \langle S, R, V, Y, Z\rangle \in \mathbf{MA}_k\), and \(\sigma\) is a rule, \(M_k\sigma = \langle S, R, V, Y', Z\rangle\) differs from \(M\) in \(Y'\), given by \(Y'(x) := Y(x) \cup \{\)conc\((\sigma)\}\) if \(\text{prem}(\sigma) \subseteq Y(x)\) and \(\sigma \in Z(x)\), and by \(Y'(x) := Y(x)\) otherwise.