A Linear Time Algorithm for Deciding Subject Security
Journal of the ACM (JACM)
On the decidability of accessibility problems (extended abstract)
STOC '00 Proceedings of the thirty-second annual ACM symposium on Theory of computing
Protection in operating systems
Communications of the ACM
The role of trust management in distributed systems security
Secure Internet programming
Introduction to Automata Theory, Languages and Computability
Introduction to Automata Theory, Languages and Computability
Introduction to Formal Language Theory
Introduction to Formal Language Theory
On complexity of grammars related to the safety problem
ICALP'06 Proceedings of the 33rd international conference on Automata, Languages and Programming - Volume Part II
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Leftist grammars can be characterized in terms of rules of the form a→ ba and cd→ d, without distinction between terminals and nonterminals. They were introduced by Motwani et. al. [9] , where the accessibility problem for some general protection system was related to the membership problem of these grammars. This protection system was originally proposed in [3,10] in the context of Java virtual worlds. We show that the set of languages defined by general leftist grammars is not included in CFL, answering in negative a question from [9]. Moreover, we relate some restricted but naturally defined variants of leftist grammars to the language classes of the Chomsky hierarchy.