FORMULAS IN MODAL LOGICS4
Katsumi Sasaki · The Review of Symbolic Logic · 2010
Here, we provide a detailed description of the mutual relation of formulas with finite propositional variablesp1, …,pmin modal logicS4. Our description contains more information onS4than those given in Shehtman (1978) and Moss (2007); however, Shehtman (1978) also treated Grzegorczyk logic and Moss (2007) treated many other normal modal logics. Specifically, we construct normal forms, which behave like the principal conjunctive normal forms in the classical propositional logic. The results include finite and effective methods to find a normal form equivalent to a given formulaAby clarifying the behavior of connectives and giving a finite method to list all exact models.