Measure and integration on Boolean algebras of regular open subsets in a topological space

The regular open subsets of a topological space form a Boolean algebra, where the join' of two regular open sets is the interior of the closure of their union. A credence’ is a finitely additive probability measure on this Boolean algebra, or on one of its subalgebras. We develop a theory of integration for such credences. We then explain the relationship between credences, residual charges, and Borel probability measures. We show that a credence can be represented by a normal Borel measure, augmented with a `liminal structure’, which specifies how two or more regular open sets share the probability mass of their common boundary. In particular, a credence on a locally compact Hausdorff space can be represented by a normal Borel measure and a liminal structure on the Stone-\v{C}ech compactification of that space. We also show how credences can be represented by Borel measures on the Stone space of the underlying Boolean algebra of regular open sets. Finally, we show that these constructions are functorial.