The core of this article is a proof that stratified Horn clause propositional systems are equivalent to and can be efficiently transformed into decision tables by a process closely related to assumption-based truth maintenance. The transformed systems execute much faster and in a bounded time, leading to the possibility of executing real-time expert systems in microseconds on fine-grained parallel computers. One consequence is to simplify the consistency and completeness analysis for such systems, in particular the problem of ambiguity. A deeper consequence is that it makes sense to view these systems as stochastic processes. This, and an analysis of the problem of maintenance of these systems, leads to the conclusion that by and large rule induction approaches are better than rule construction approaches for building them. 0 1995 John Wiley & Sons, Inc.