A Question about Hierarchical Systems

The control of large systems is always organized in a distributed hierarchy. We discuss two approaches to understanding such a hierarchy. The approach propagated by work in verification adopts a “one-world” semantics in which syntactical constructs at higher levels are “compiled” into a single interpretation at the lowest level. Many hierarchical systems, however, are designed and analyzed using a “multi-world” semantics, with a separate interpretation at each level. One-world semantics offers a sound way of stating and proving claims about the system, but multi-world semantics better conforms to practice. The paper poses the question: how to join the theoretical advantages of one-world semantics to the practical convenience of multi-world semantics.