Succinct representation of regular languages by boolean automata

Boolean automata are a generalization of finite automata in the sense that the ‘next state’, i.e. the result of the transition function given a state and a letter, is not just a single state (deterministic automata) or a union of states (nondeterministic automata) but a boolean function of states. Boolean automata accept precisely regular languages; furthermore they correspond in a natural way to certain language equations as well as to sequential networks. We investigate the succinctness of representing regular languages by boolean automata. In particular, we show that for every deterministic automaton A with m states there exists a boolean automaton with [log₂m] states which accepts the reverse of the language accepted by A (m≥1). We also show that for every n≥1 there exists a boolean automation with n states such that the smallest deterministic automaton accepting the same language has 2⁽²ⁿ⁾ states; moreover this holds for an alphabet with only two letters.     

Concise representations of regular languages by degree and probabilistic finite automata

Meyer and Fischer b][MF] proved that nondeterministic finite automata (NFA) can be exponentially more concise than deterministic finite automata (DFA) in their representations of regular languages. Several variants of that basic finite state machine model are now being used to analyze parallelism and to build real-time software systems [HL+]. Even though these variants can sometimes represent regular languages in a more concise manner than NFA, the underlying models fundamentally differ from NFA in how they operate. Degree automata [W] (DA), however, differ from NFA only in their acceptance criteria and accept only regular languages. We show here that DA are also exponentially more concise than NFA on some sequences of regular languages. We also show that the conciseness of probabilistic automata [R] with isolated cutpoints can be unbounded over DA and, concurrently, i.e., over the same sequence of languages, those DA can be exponentially more concise than NFA.Detlef Wotschke was supported in part by Deutsche Forschungsgemeinschaft under Grant No. Wo 334/2-1 and by Stiftung Volkswagenwerk under Grant No. II/62 325.     

On a class of languages recognizable by probabilistic reversible decide-and-halt automata

We analyze the properties of probabilistic reversible decide-and-halt automata (DH-PRA) and show that there is a strong relationship between DH-PRA and 1-way quantum automata. We show that a general class of regular languages is not recognizable by DH-PRA by proving that two “forbidden” constructions in minimal deterministic automata correspond to languages not recognizable by DH-PRA. The shown class is identical to a class known to be not recognizable by 1-way quantum automata. We also prove that the class of languages recognizable by DH-PRA is not closed under union and other non-trivial Boolean operations.     

More concise representation of regular languages by automata and regular expressions

We consider two formalisms for representing regular languages: constant height pushdown automata and straight line programs for regular expressions. We constructively prove that their sizes are polynomially related. Comparing them with the sizes of finite state automata and regular expressions, we obtain optimal exponential and double exponential gaps, i.e., a more concise representation of regular languages.     

Realizations of fuzzy languages by probabilistic,max-product,and maximin automata

In this paper, the classes of fuzzy languages realized by probabilistic, max-product and maximin automata are examined. Simple characterizations of these classes are given which reduce to Nerode's Theorem in the deterministic case. Using these characterizations, various properties of these classes of fuzzy languages are derived, including closure properties under various types of operations.     

Closure properties and languages defined by bilinear automata

In this paper we define bilinear languages, via cutpoints and bilinear automata, and we obtain a necessary condition for a bilinear language to be regular. We also prove that there exists a bilinear language which is nonstochastic.     

Non-deterministic cellular automata and languages

We summarize results on non-deterministic cellular language acceptors. The non-determinism is regarded as limited resource. For parallel devices, it is natural to bound the non-determinism in time and/or space. Depending on the length of the input, the number of allowed non-deterministic state transitions as well as the number of non-deterministic cells at all is limited. We centre our attention to real-time, linear-time, and unrestricted-time computations and discuss the computational power of these machines. Speed-up results and the possibility to reduce the non-determinism as well as closure properties of languages acceptable with a constant number of non-deterministic transitions are presented. By considering the relations with context-free languages, several relations between the devices in question are implied. We do not prove these results but we merely draw attention to the big picture and some of the main ideas involved, and open problems for further research.     

On probabilistic analog automata

We consider probabilistic automata on a general state space and study their computational power. The model is based on the concept of language recognition by probabilistic automata due to Rabin (Inform. Control 3 (1963) 230) and models of analog computation in a noisy environment suggested by Maass and Orponen (Neural Comput. 10 (1998) 1071), and Maass and Sontag (Neural Comput. 11 (1999) 771). Our main result is a generalization of Rabin's reduction theorem that implies that under very mild conditions, the computational power of such automata is limited to regular languages.