Showing papers by "Kamala Krithivasan published in 2002"

Contextual P Systems

Abstract: Generally, in P systems with string-objects one uses the Chomsky way of rewriting for processing the objects. In this paper we consider the contextual way of handling string-objects in P systems. We introduce some variants of contextual grammars and prove that contextual P systems with rules corresponding to these variants are more powerful than ordinary contextual grammars and their variants. We also show that one-sided contextual P systems with right-sided erased contexts and insertion contextual P systems with right-sided erased contexts are computationally complete.

A Note on Hybrid P Systems

Abstract: Generally, in rewriting P systems (Martin-Vide and Paun, 2000) one uses Chomsky rules (Hopcroft and Ullman, 1979), whereas in contextual P systems (Madhu and Krithivasan, 2002) we considered contextual rules (Marcus, 1969), (Paun, 1997) for processing string-objects. By combining Chomsky rules and contextual rules, a new class of P systems were introduced in Krishna et al. (2001), the hybrid P systems. In this paper we continue the study of hybrid P systems, and show that systems with two membranes are universal in the case of contextual rules with a regular choice, and systems with four membranes are universal in the case of contextual rules with finite selection.

A Survey of Some Variants of P Systems

Abstract: In this paper we give a brief survey of some variants of P systems and their computational capacity. An improvement of a known result about rewriting P systems with leftmost derivation is given. We also give the generalized definition for normal forms of rewriting P systems.

Generalized normal form for rewriting P systems

Abstract: P systems, introduced by Gh. Paun [9] as a new theoretical model for molecular computations, are based on the notion of membrane structure. Several variants of P systems have been proposed and shown to be computationally universal. One of such variant is the rewriting P systems, where we consider string-objects and process them using rewriting rules. Particular cases of normal forms for rewriting P systems were proposed in [11–13]. In this work we introduce the generalized normal form for rewriting P systems which take into consideration the depth of the membrane structure and the number of rewriting rules present in each membrane. Such generalized normal forms are given for rewriting P systems with priorities, and for partially parallel rewriting P systems. In this way, several results from the literature are generalized and improved.

On rule-number complexity of components of probabilistic cooperating distributed grammar systems

Abstract: In this paper we discuss a size property of Probabilistic Cooperating Distributed Grammar Systems, grammatical constructs designed for modelling distributed random processing. We show that, with respect to the number of productions of a component grammar as a complexity measure, these systems exhibit a language specification of low complexity.

Probabilistic Parallel Communicating Grammar Systems

Abstract: Grammar systems are theoretical models of distributed computing which play a major role in modern Computer Science. In this paper, we define and study a variant of Parallel Communicating(PC) grammar systems namely, Probabilistic PC grammar systems which serves as a grammatical model for random distributed processing. We study the construct with two different models of communication protocols namely, communication by request and communication by command. We explore the generative capacity of the variant with regular, context-free and context-sensitive rules in both models of communication.