Abstract

Two things are done in this paper. First, a modal logic in which one can quantify over both objects and concepts is presented; a semantics and a tableau system are given. It is a natural modal logic, extending standard versions, and capable of addressing several well-known philosophical difficulties successfully. Second, this modal logic is used to introduce a rather different way of looking at relational databases. The idea is to treat records as possible worlds, record entries as objects, and attributes as concepts, in the modal sense. This makes possible an intuitively satisfactory relational database theory. It can be extended, by the introduction of higher types, to deal with multiple-valued attributes and more complex things, though this is further than we take it here.