 The set of formulas of \(\Delta\) that are valid in a class of models \(\mathcal{M}\) is denoted \(\Delta_{\mathcal{M}}\) (for frames the denotation is \(\Delta_{\mathcal{F}}\)). For a set of formulas \(\Sigma\), we write \(M,w \models \Sigma\) to say that \(M,w \models \sigma\), for all \(\sigma\in \Sigma\). We say that a set of formulas \(\Sigma\) semantically entails a formula \(\varphi\) in a class of models \(\mathcal{M}\), denoted \(\Sigma \models_{\mathcal{M}} \varphi\), if for every \(M \in \mathcal{M}\) we have that \(\models_{M} \Sigma\) implies \(\models_{M} \varphi\).