Bisimulations for fuzzy automata

Bisimulations have been widely used in many areas of computer science to model equivalence between various systems, and to reduce the number of states of these systems, whereas uniform fuzzy relations have recently been introduced as a means to model the fuzzy equivalence between elements of two possible different sets. Here we use the conjunction of these two concepts as a powerful tool in the study of equivalence between fuzzy automata. We prove that a uniform fuzzy relation between fuzzy automata A and B is a forward bisimulation if and only if its kernel and co-kernel are forward bisimulation fuzzy equivalence relations on A and B and there is a special isomorphism between factor fuzzy automata with respect to these fuzzy equivalence relations. As a consequence we get that fuzzy automata A and B are UFB-equivalent, i.e., there is a uniform forward bisimulation between them, if and only if there is a special isomorphism between the factor fuzzy automata of A and B with respect to their greatest forward bisimulation fuzzy equivalence relations. This result reduces the problem of testing UFB-equivalence to the problem of testing isomorphism of fuzzy automata, which is closely related to the well-known graph isomorphism problem. We prove some similar results for backward-forward bisimulations, and we point to fundamental differences. Because of the duality with the studied concepts, backward and forward-backward bisimulations are not considered separately. Finally, we give a comprehensive overview of various concepts on deterministic, nondeterministic, fuzzy, and weighted automata, which are related to bisimulations.     

直觉模糊有限自动机的乘积

给出了直觉模糊有限自动机的广义直积、级联积和圈积及覆盖的定义,讨论了直觉模糊有限自动机在同构意义下级联积和圈积满足结合性以及各种乘积之间的覆盖关系。     

模糊Rabin自动机和模糊Game自动机的等价性

自动机是理论计算机的一个重要的研究内容.模糊Rabin自动机和模糊Game自动机是经典自动机的延续,给出了模糊Rabin自动机和模糊Game自动机的相关定义,讨论各自的内在性质,并得到了二者的等价关系.这进一步丰富了模糊自动机理论.     

模糊自动机的强连通性及群自动机

为了更好地研究模糊自动机的结构和性质,采用代数的方法,在传统的模糊有限状态自动机的基础上,通过定义状态集合为代数群的自动机,讨论了这一类自动机的连通性和正则性,这丰富了模糊自动机理论．     

幺半环上几类模糊自动机的关系

给出了幺半环上非确定的模糊自动机和确定的模糊自动机及其语言的定义,证明了幺半环上三类非确定的模糊自动机间的等价性和三类确定的模糊自动机间的等价性,讨论了幺半环上三类非确定的模糊自动机和第四类非确定的模糊自动机之间的关系,以及幺半环上非确定的模糊自动机和确定的模糊自动机之间的关系.     

具有输出字符功能的模糊自动机的最小化问题

通过文献[8]中两类具有输出字符功能的Fuzzy自动机和Fuzzy有限状态自动机的强等价性,等价性和弱等价性的条件,在以往仅仅给出的Fuzzy有限状态自动机的最小化问题基础上,讨论了具有更广泛意义的具有输出字符功能的Fuzzy自动机的最小化问题,以及其最小化自动机与Fuzzy有限状态自动机的最小化自动机在不同条件下的关系。     

New directions in fuzzy automata

Automata are the prime example of general computational systems over discrete spaces. The incorporation of fuzzy logic into automata theory resulted in fuzzy auotomata which can handle continuous spaces. Moreover, they are able to model uncertainty which is inherent in many applications. Deterministic Finite-state Automata (DFA) have been the architecture, most used in many applications, but, the increasing interest in using fuzzy logic for many new areas necessitates that the formalism of fuzzy automata be more developed and better established to fulfill implementational requirements in a well-defined manner. This need is due to the fact that despite the long history of fuzzy automata and lots of research being done on that, there are still some issues which have not been well-established and issues which need some kind of revision. In particular, we focus on membership assignment, output mapping, multi-membership resolution, and the concept of acceptance for fuzzy automata. We develop a new general definition for fuzzy automata, and based on that, develop well-defined and application-driven methodologies to establish a better ground for fuzzy automata and pave the way for forthcoming applications.     

Fuzzy automata and life

Boolean cellular automata may be generalized to fuzzy automata in a consistent manner. Several fuzzy logics are used to create 1‐dimensional automata and also 2‐dimensional automata that generalize the game of life. These generalized automata are investigated and compared to their Boolean counterparts empirically and using rule entropy and repeated input response functions. Fuzzy automata offer new mechanisms for classification of classical automata and can be used for insight into their qualitative behavior. © 2002 Wiley Periodicals, Inc.     

模糊无限状态自动机及其收敛性

到目前为止,我们所研究的模糊或非模糊的自动机都是有限状态自动机.然而,关于无限状态自动机的定义及它的稳定性和收敛性都没有被讨论过.本文中,我们使用离散的反馈神经网络及网络输出空间划分方法,同时,在梯度更新算法中使用伪梯度方法,给出了模糊无限状态自动机收敛到模糊有限状态自动机的证明.     

On minimal realization of fuzzy behaviour and associated categories

This paper is towards the study of minimal deterministic automata with fuzzy output which realizes the given fuzzy behaviour. The construction of such automaton is based on Myhill-Nerode’s theory, and it is shown that this automaton is a canonical realization of given fuzzy behaviour. Meanwhile, we introduce the categories of deterministic automata with fuzzy output and fuzzy behaviour. The relationship between both the categories through functors is also studied.     

Minimization algorithm of fuzzy finite automata

In this paper, a class of fuzzy finite automata corresponding to the Mealy type of ordinary automata is formulated, and also two types of statewise equivalence relations are introduced. From the equivalence relations, a minimal form is defined and a minimization algorithm of the Mealy type of fuzzy finite automata is obtained.     

模糊有限自动机的乘积覆盖性

推广模糊有限自动机的有限积,包括direct infinite乘积、cascade infinite乘积和wreath infinite 来积.进而讨论它们之间的关系,得到乘积覆盖性等代数性质.     

基于模糊字符串的Mealy格值有限自动机及其最小化

提出取值为格半群的Mealy格值有限自动机的概念,进而得到基于模糊字符串的Mealy格值有限自动机的扩张模型,并较详细讨论了其性质. 同时定义了扩张的完备Mealy格值有限自动机的行为矩阵, 在此基础上给出了其最小化算法.     

Stock market forecasting by using a hybrid model of exponential fuzzy time series

The initial aim of this study is to propose a hybrid method based on exponential fuzzy time series and learning automata based optimization for stock market forecasting. For doing so, a two-phase approach is introduced. In the first phase, the optimal lengths of intervals are obtained by applying a conventional fuzzy time series together with learning automata swarm intelligence algorithm to tune the length of intervals properly. Subsequently, the obtained optimal lengths are applied to generate a new fuzzy time series, proposed in this study, named exponential fuzzy time series. In this final phase, due to the nature of exponential fuzzy time series, another round of optimization is required to estimate certain method parameters. Finally, this model is used for future forecasts. In order to validate the proposed hybrid method, forty-six case studies from five stock index databases are employed and the findings are compared with well-known fuzzy time series models and classic methods for time series. The proposed model has outperformed its counterparts in terms of accuracy.     

Sequential fuzzy system identification

The problem of deriving the structure of a non-deterministic system from its behaviour is a difficult one even when that behaviour is itself well-defined. When the behaviour can be described only in fuzzy terms structural inference may appear virtually impossible. However, a rigorous formulation and solution of the problem for stochastic automata has recently been given [1] and, in this paper, the results are extended to fuzzy stochastic automata and grammars. The results obtained are of interest on a number of counts. (1) They are a further step towards an integrated ‘theory of uncertainty’; (2) They give new insights into problems of inductive reasoning and processes of ‘precisiation’; (3) They are algorithmic and have been embodied in a computer program that can be applied to the modelling of sequential fuzzy data; (4) They demonstrate that sequential fuzzy data may be modelled naturally in terms of ‘possibility’ vectors.     

模糊有限自动机两个算子的若干性质

在文[1]定义了模糊有限自动机的bifuzzy seccessor算子和bifuzzy source算子的基础上,着重研究它们之间的基本性质及关系,并得到几个重要的性质定理。     

The Equivalence of the DFA and OFA Automate

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Quantaloids,enriched categories and automata theory

This article is intended to be an survey article outlining how the theory of quantaloids and categories enriched in them provides an effective means of analyzing both automata and tree automata. The emphasis is on the unification of concepts and how categorical methods provide insight into various calculations and theorems, both illuminating the original presentation as well as yielding conceptually simpler proofs. Proofs will be omitted and the emphasis is on providing the reader (even a relatively inexperienced one) with an understanding of the basic constructions and results.     

Lattice valued relations and automata

A lattice-valued relation, lvr for short, from a set X to a set Y is a function from the Cartesian product of X and Y to a lattice. This concept is a generalization of other structures, notably tolerance spaces, nets and automata, separately investigated by the authors elsewhere. It is adequate to admit a natural definition of homogeneity and a classification of homogeneous lvr's by their isomorphism groups. The main result of the present paper is a proof of this classification. The application of this to automata, also interpretable as lvr's, is described, and an example given. We conclude with a brief discussion of the lvr theory of fuzzy and stochastic automata.     

On Inverse Limits and Direct Limits for Fuzzy Topological Spaces

Li has introduced the concepts of inverse system and direct system for fuzzy topological spaces and studied inverse limits and direct limits on such spaces by presenting the explicit constructions of these limits.In this paper some important concepts of fuzzy topology,such as,product fuzzy topology,quotient fuzzy topology,fuzzy continuity etc.,are used for further study of inverse limits and direct limits for fuzzy topological spaces.