 Informally, the underlying set \(W\) is a set of situations, and \(R\) is an accessibility relation connecting situations. All the terms are interpreted as sets of situations, and function application is the existential image operation derived from \(R\). A difference from the previous models is that the result of an application of a term to a term is not determined by the objects themselves that interpret the two terms—rather the application operation is defined from \(R\).