 Kraus, Lehmann, and Magidor (1990) focused on a particular class of cumulative models, the so-called preferential models. They require the binary relation to be a strict partial order and the labeling function to assign just one world to each state. A preferential model for a universe \(W\) is a triple \(\langle S, l, &lt; \rangle\) where \(S\) is a set of states, \(l: S \rightarrow W\) is a labeling function assigning to each state a single world from the universe \(W\), and \(&lt;\) is a strict partial order on \(S\) (irreflexive, transitive) satisfying the smoothness condition.