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Durham University

Computer Science


Publication details for Professor Iain Stewart

Stewart, I.A. (2002). Program schemes, arrays, Lindstroem quantifiers and zero-one laws. Theoretical Computer Science 275(1-2): 283-310.

Author(s) from Durham


We characterize the class of problems accepted by a class of program schemes with arrays, NPSA, as the class of problems defined by the sentences of a logic formed by extending first-order logic with a particular uniform (or vectorized) sequence of Lindström quantifiers. A simple extension of a known result thus enables us to prove that our logic, and consequently our class of program schemes, has a zero-one law. However, we use another existing result to show that there are problems definable in a basic fragment of our logic, and so also accepted by basic program schemes, which are not definable in bounded-variable infinitary logic. As a consequence, the class of problems NPSA is not contained in the class of problems defined by the sentences of partial fixed-point logic even though in the presence of a built-in successor relation, both NPSA and partial fixed-point logic capture the complexity class PSPACE.