 Description logics are essentially variations of modal logics. They involve concepts (unary predicates) and roles (binary predicates) and are used to describe various ontologies and the relations between the concepts in them (see e.g. Baader and Lutz 2006). Description logics can be temporalized in various ways. For details, see Artale and Franconi (2000); Wolter and Zakharyaschev (2000); and Lutz et al. (2008).