The relation between sentences and what they describe is an important theoretical and practical representational issue. This issue comprises two primary components: An ontological issue about what the major classes of entities to be represented are, and a formal issue of how best to represent them. Some semantic network systems make a point of providing entities corresponding to propositions, and some provide entities corresponding to situations, although the distinction between the two is sometimes confused. Both propositions and situations are useful, but for quite different purposes. Also, the representation of situations and propositions can be done in various ways, some of which have important representational advantages.

Situations on the whole have been relatively neglected. When they are provided at all, the ontology of situations has generally been too limited. One way to overcome these limitations is to introduce an operator that associates a situation with any logical sentence, as advocated by Schubert and Hwang (1989). Unfortunately, such an approach appears to introduce serious difficulties.

Instead, I suggest that the best solution is simply to extend the usual ontology of situations somewhat, while maintaining a separate set of entities that correspond to propositions. The components of this proposal are by and large familiar. However, considering them together gives a somewhat novel picture. For example, it seems that the notion of intensions becomes unnecessary. Some of the implications of an extended ontology of situations are explored, including the relation of propositions to situations and the notion of equality of situations.