Properties that characterize LOGCFL

doi:10.1016/0022-0000(91)90020-6

Journal of Computer and System Sciences

Volume 43, Issue 2, October 1991, Pages 380-404

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Abstract

Two properties, called semi-unboundedness and polynomial proof-size, are identified as key properties shared by the definitions of LOGCFL on several models of computations. The semi-unboundedness property leads to the definition of semi-unbounded fan-in circuit families. These are circuits obtained from unbounded fan-in circuits by restricting the fan-in of gates of one type. A new characterization of LOGCFL is obtained on such a model in which the fan-in of the AND gates are bounded by a constant. This property also suggests new characterizations of LOGCFL on the following models: alternating Turing machines, nondeterministic auxiliary pushdown automata, and bounded fan-in Boolean circuits.

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: Most of this work was supported by the National Science Foundation under Grants DCR-8301212 and DCR-8352093 while the author was at the University of Washington, Seattle. A preliminary version of this paper was presented at the 19th Annual Symposium on Theory of Computing, New York, 1987.