Recursively enumerable language

About: Recursively enumerable language is a research topic. Over the lifetime, 1508 publications have been published within this topic receiving 32382 citations.

Learning of R.E. Languages from Good Examples

Abstract: The present paper investigates identification of indexed families of recursively enumerable languages from good examples. In the context of class preserving learning from good text examples, it is shown that the notions of finite and limit identification coincide. On the other hand, these two criteria are different in the context of class comprising learning from good text examples. In the context of learning from good informant examples, finite and limit identification criteria differ for both class preserving and class comprising cases. The above results resolve an open question posed by Lange, Nessel and Wiehagen in a similar study about indexed families of recursive languages.

The power of alternating one-reversal counters and stacks

Abstract: The relation between reversals and alternation is studied in two simple models of computation: the 2-counter machine with a one-way input tape whose counters make only one reversal (1-reversal 2CM) and the one-way pushdown automaton whose pushdown store makes only one reversal (1-reversal PDA). The following is shown: (a) alternating 1-reversal 2CM’s accept all recursively enumerable languages; (b) alternating 1-reversal PDA’s accept exactly the languages accepted by exponential time-bounded deterministic TM’s. The first improves on the known result that alternating 1-reversal 4CM’s accept all recursively enumerable languages. The second improves an earlier result that alternating PDA’s with no restrictions on reversals accept exactly the exponential-time languages.

Rule-restricted automaton-grammar transducers: power and linguistic applications

Abstract: This paper introduces the notion of a new transducer as a two-component system, which consists of a nite automaton and a context-free grammar. In essence, while the automaton reads its input string, the grammar produces its output string, and their cooperation is controlled by a set, which restricts the usage of their rules. From a theoretical viewpoint, the present paper discusses the power of this sys- tem working in an ordinary way as well as in a leftmost way. In addition, the paper introduces an appearance checking, which allows us to check whether some symbols are present in the rewritten string, and studies its eect on the power. It achieves the following three main results. First, the system generates and accepts languages dened by matrix grammars and partially blind multi-counter automata, respec- tively. Second, if we place a leftmost restriction on derivation in the context-free grammar, both accepting and generating power of the system is equal to generative power of context-free grammars. Third, the system with appearance checking can accept and generate all recursively enumerable languages. From more pragmatical viewpoint, this paper describes several linguistic applications. A special attention is paid to the Japanese-Czech translation.

Equivalence of Subclasses of Two-Way Non-Deterministic Watson Crick Automata

Abstract: Watson Crick automata are finite automata working on double strands. Extensive research work has already been done on non deterministic Watson Crick automata and on deterministic Watson Crick automata. Parallel Communicating Watson Crick automata systems have been introduced by E. Czeziler et al. In this paper we discuss about a variant of Watson Crick automata known as the two-way Watson Crick automata which are more powerful than non-deterministic Watson Crick automata. We also establish the equivalence of different subclasses of two-way Watson crick automata. We further show that recursively enumerable (RE) languages can be realized by an image of generalized sequential machine (gsm) mapping of two-way Watson-Crick automata.