Reliable computer systems must handle malfunctioning components that give conflicting information to different parts of the system. This situation can be expressed abstractly in terms of a group of generals of the Byzantine army camped with their troops around an enemy city. Communicating only by messenger, the generals must agree upon a common battle plan.… (More)
The problem addressed here concerns a set of isolated processors, some unknown subset of which may be faulty, that communicate only by means of two-party messages. Each nonfaulty processor has a private value of information that must be communicated to each other nonfaulty processor. Nonfaulty processors always communicate honestly, whereas faulty… (More)
A method ~s g~ven for dec~dlng formulas in combinations of unquantified first-order theories. Rather than couphng separate decision procedures for the contributing theories, the method makes use of a single, uniform procedure that minimizes the code needed to accommodate each additional theory. It ~s apphcable to theories whose semantics can be encoded… (More)
V R Pratt has shown that the real and integer feastbdlty of sets of linear mequallUes of the form x _< y + c can be decided quickly by examining the loops m certain graphs Pratt's method is generahzed, first to real feaslbdlty of mequahues m two variables and arbitrary coefficients, and ultimately to real feaslbdlty of arbitrary sets of hnear mequahtles The… (More)
A simple technique for reasoning about equalities that is fast and complete for ground formulas with function symbols and equality is presented. A proof of correctness is given as well.
A practical procedure is presented for an extension of quantifier-free Presburger arithmetic that permits arbitrary unmterpreted predicate and function symbols This theory includes many of the formulas one tends to encounter in program venficatlon and is powerful enough to encode the semantics of array operators as well as MAX, MIN, and ABSVALUE An… (More)
This article presents an improved version of Bledsoe's SUP-INF method for proving theorems in a subclass of Presburger arithmetic The improved method is able to determine mvahdRy as well as vahdlty, and provides counterexamples for formulas determined to be mvahd A proof of correctness is given for the algorithms on which the method is based Implementation… (More)