Joseph Y. Halpern, Yoram Moses
Journal of the ACM
An operator precedence language which is not real-time definable by any multitple Turing machine is constructed. This strengthens previous results about the existence of unambiguous context-free languages (CFL's) which are not real-time definable. In contrast, a family of CFL's of increasing degree of inherent ambiguity, each real-time definable by a one-tape Turing machine, is exhibited. In fact, an unboundedly ambiguous CFL, also real-time definable by a one-tape Turing machine, is presented. These results are the basis for the assertion that real-time definability of a CFL is independent from each of the structural properties considered. © 1968, ACM. All rights reserved.
Joseph Y. Halpern, Yoram Moses
Journal of the ACM
Michael Factor, Dafna Sheinwald
Information Sciences
Bing Zhang, Mikio Takeuchi, et al.
ICAIF 2024
Ronald Fagin
Journal of the ACM