Formal methods hold the promise for high dependability in the design of critical software.
However, software engineers who employ formal methods need to communicate their design decisions to users, customers, managers, and colleagues who may not be in a position to acquire a full understanding of the formal notation being used. Visualizations derived from formal specifications and designs must be able convey the required information precisely and reliably without the use of formal notation. The emphasis is placed on how to convey graphically various kinds of formally-stated program properties. The illustrations are extracted from a case study involving the formal derivation of a message router. The ultimate goal is to identify issues fundamental to the use of visualization in conjunction with formal methods and to catalog methods which achieve effective visual communication without compromising formal reasoning.