  Whether explicit or implicit, sets are a critical part of many pieces of
software. As a result, it is necessary to develop abstractions of sets for the
purposes of abstract interpretation, model checking, and deductive
verification. However, the construction of effective abstractions for sets is
challenging because they are a higher-order construct. It is necessary to
reason about contents of sets as well as relationships between sets. This paper
presents a new abstraction for sets that is based on binary decision diagrams.
It is optimized for precisely and efficiently representing relations between
sets while still providing limited support for content reasoning.
