Latest Articles from JUCS - Journal of Universal Computer Science Latest 88 Articles from JUCS - Journal of Universal Computer Science https://lib.jucs.org/ Fri, 29 Mar 2024 09:54:55 +0200 Pensoft FeedCreator https://lib.jucs.org/i/logo.jpg Latest Articles from JUCS - Journal of Universal Computer Science https://lib.jucs.org/ Knowledge Geometry in Phenomenon Perception and Artificial Intelligence https://lib.jucs.org/article/24075/ JUCS - Journal of Universal Computer Science 26(5): 604-623

DOI: 10.3897/jucs.2020.032

Authors: João Gabriel Lopes De Oliveira, Pedro Moreira Menezes Da Costa, Flavio De Mello

Abstract: Artificial Intelligence (AI) pervades industry, entertainment, transportation, finance, and health. It seems to be in a kind of golden age, but today AI is based on the strength of techniques that bear little relation to the thought mechanism. Contemporary techniques of machine learning, deep learning and case-based reasoning seem to be occupied with delivering functional and optimized solutions, leaving aside the core reasons of why such solutions work. This paper, in turn, proposes a theoretical study of perception, a key issue for knowledge acquisition and intelligence construction. Its main concern is the formal representation of a perceived phenomenon by a casual observer and its relationship with machine intelligence. This work is based on recently proposed geometric theory, and represents an approach that is able to describe the inuence of scope, development paradigms, matching process and ground truth on phenomenon perception. As a result, it enumerates the perception variables and describes the implications for AI.

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Research Article Thu, 28 May 2020 00:00:00 +0300
Cancer Classification by Gene Subset Selection from Microarray Dataset https://lib.jucs.org/article/23292/ JUCS - Journal of Universal Computer Science 24(6): 682-710

DOI: 10.3217/jucs-024-06-0682

Authors: Asit Das, Soumen Pati, Hsien-Hung Huang, Chi-Ken Chen

Abstract: Microarray dataset contains huge number of genes, many of which are irrelevant regarding cancer classification and as a result classification accuracy is reduced. Therefore, the dataset should be pre-processed to filter out these redundant genes. In this paper, initially a Pareto optimality based Multi-objective Genetic Algorithm has been proposed where non-linear cellular automata is employed to overcome the demerits of random initialization to generate initial population in high dimensional space. The fitness functions are defined based on both attribute dependency and boundary region exploration of rough set theory and Log-Likelihood ratio to select the informative genes. The chromosomes are hybridized by applying multi-point crossover; whereas proximity mutation builds on Flip-bit mutation with a little modification to produce fittest offspring. Finally, the gene subset with strong biological significance in cancer treatment is obtained from the Pareto dominant solutions. Performances are investigated on publicly available microarray cancer datasets and compared with the state-of-the-art methods to demonstrate the effectiveness of the proposed method.

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Research Article Thu, 28 Jun 2018 00:00:00 +0300
Reversibility in Parallel Rewriting Systems https://lib.jucs.org/article/23373/ JUCS - Journal of Universal Computer Science 23(7): 692-703

DOI: 10.3217/jucs-023-07-0692

Authors: Bogdan Aman, Gabriel Ciobanu

Abstract: This paper represents a study of reversibility in parallel rewriting systems over multisets. It emphasizes the controlled reversibility for a particular case of parallel rewriting systems given by membrane systems, a formalism inspired by the cell activity. We define reversible membrane systems in which the scenarios based on regular expressions are able to control the direction (forward or backward) of the evolution. The backward computation is triggered by a special symbol ae introduced into the system. Several results concerning the evolution of membrane systems and reversible membrane systems are provided, opening new research opportunities.

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Research Article Fri, 28 Jul 2017 00:00:00 +0300
The Least ∑-jump Inversion Theorem for n-families https://lib.jucs.org/article/23285/ JUCS - Journal of Universal Computer Science 23(6): 529-538

DOI: 10.3217/jucs-023-06-0529

Authors: Marat Faizrahmanov, Iskander Kalimullin, Antonio Montalban, Vadim Puzarenko

Abstract: Studying the ∑-reducibility of families introduced by [Kalimullin and Puzarenko 2009] we show that for every set there is a family of sets which is the ∑-least countable family whose ∑-jump is ∑-equivalent to . This fact will be generalized for the class of n-families (families of families of ... of sets).

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Research Article Wed, 28 Jun 2017 00:00:00 +0300
Communication in Abstract State Machines https://lib.jucs.org/article/22976/ JUCS - Journal of Universal Computer Science 23(2): 129-145

DOI: 10.3217/jucs-023-02-0129

Authors: Egon Börger, Klaus-Dieter Schewe

Abstract: Up to recently the majority of applications of the Abstract State Machines method for design and verification of computational systems used the shared variable approach. However in particular with distributed systems only various forms of communication may be available to share information. We define communicating ASMs by using instead of shared locations an explicit, abstract concept of Sending/Receiving messages which can be added to existing ASM execution engines. We aim to provide a definition which is a conservative extension of traditional ASMs, uniformly captures synchronous and asynchronous communication and is not bound to any specific message passing mechanism but can be instantiated to the major communication concepts in the literature. We illustrate the concept by an application to synchronous and asynchronous networks of communicating processes.

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Research Article Tue, 28 Feb 2017 00:00:00 +0200
The Enumeration Spectrum Hierarchy of α-families and Lowα Degrees https://lib.jucs.org/article/23355/ JUCS - Journal of Universal Computer Science 22(7): 943-955

DOI: 10.3217/jucs-022-07-0943

Authors: Marat Faizrahmanov, Iskander Kalimullin

Abstract: In this paper we introduce a hierarchy of families which can be derived from the integers using countable collections. This hierarchy coincides with the von Neumann hierarchy of hereditary countable sets in the ZFC-theory with urelements from ℕ. The families from the hierarchy can be coded into countable algebraic structures preserving their algorithmic properties. We prove that there is no maximal level of the hierarchy and that the collection of non-lowα degrees for every computable ordinal ff is the enumeration spectrum of a family from the hierarchy. In particular, we show that the collection of non-lowα degrees for every computable limit ordinal α is a degree spectrum of some algebraic structure.

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Research Article Fri, 1 Jul 2016 00:00:00 +0300
A Taxonomy of Minimisation Algorithms for Deterministic Tree Automata https://lib.jucs.org/article/22967/ JUCS - Journal of Universal Computer Science 22(2): 180-196

DOI: 10.3217/jucs-022-02-0180

Authors: Johanna Björklund, Loek Cleophas

Abstract: We present a taxonomy of algorithms for minimising deterministic bottomup tree automata (dtas) over ranked and ordered trees. Automata of this type and its extensions are used in many application areas, including natural language processing (nlp) and code generation. In practice, dtas can grow very large, but minimisation keeps things manageable. The proposed taxonomy serves as a unifying framework that makes algorithms accessible and comparable, and as a foundation for efficient implementation. Taxonomies of this type are also convenient for correctness and complexity analysis, as results can frequently be propagated through the hierarchy. The taxonomy described herein covers a broad spectrum of algorithms, ranging from novel to well-studied ones, with a focus on computational complexity.

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Research Article Mon, 1 Feb 2016 00:00:00 +0200
Deterministic Frequency Pushdown Automata https://lib.jucs.org/article/23750/ JUCS - Journal of Universal Computer Science 21(12): 1563-1576

DOI: 10.3217/jucs-021-12-1563

Authors: Cristian S. Calude, Rūsiņš Freivalds, Sanjay Jain, Frank Stephan

Abstract: A set L is (m, n)-computable iff there is a mechanism which on input of n different words produces n conjectures whether these words are in L, respectively, such that at least m of these conjectures are right. Prior studies dealt with (m, n)- computable sets in the contexts of recursion theory, complexity theory and the theory of finite automata. The present work aims to do this with respect to computations by deterministic pushdown automata (using one common stack while processing all input words in parallel). We prove the existence of a deterministic context-free language L which is recognised by an (1, 1)-DPDA but fails to be recognised by any (m, n)-DPDA, where n ≥ 2 and m ≥ n/2+1. This answers a question posed by Eli Shamir at LATA 2013. Furthermore, it is shown that there is a language L such that, for all m, n with m ≤ n/2, L can be recognised by an (m, n)-DPDA but, for all m, n with 1 ≤ m ≤ n, L cannot be recognised by (m, n)-DFA.

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Research Article Tue, 1 Dec 2015 00:00:00 +0200
Heuristic Algorithms for Manufacturing and Replacement Strategies of the Production System https://lib.jucs.org/article/23110/ JUCS - Journal of Universal Computer Science 21(4): 503-525

DOI: 10.3217/jucs-021-04-0503

Authors: Robert Bucki, Bronislav Chramcov, Petr Suchánek

Abstract: The paper highlights the problem of minimizing economic costs of making orders in the automated manufacturing system which consists of work centres arranged in a series. Each of them is equipped with tools which carry out defined manufacturing operations. Tools are replaced with new ones only when no manufacturing operation can be performed any more in order to minimize the residual pass. The equations of state of the production line are presented and heuristic control strategies are discussed in detail. The criterion is to minimize the number of replacement procedures which results in maximizing the use of tools in work centres. To prove the correctness of the presented approach the paper is supported with an extended simulation study based on implementing available combinations of either manufacturing or replacement strategies taking into account various configurations which come into being in the real manufacturing environment. The simulation results form the basis for the detailed analysis to meet the requirements of the applicable decision-making procedures.

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Research Article Wed, 1 Apr 2015 00:00:00 +0300
Formal Study of Routing Protocols for Wireless Sensor Networks https://lib.jucs.org/article/23493/ JUCS - Journal of Universal Computer Science 20(9): 1373-1401

DOI: 10.3217/jucs-020-09-1373

Authors: José Mateo, María del Carmen Ruiz, Hermenegilda Maciá, Juan Pardo

Abstract: NORA (Network rOle-based Routing Algorithm) and NORIA (Network rOle-based Routing Intelligent Algorithm) are novel routing algorithms for Wireless Sensor Networks (WSNs), which combine various effective techniques in order to reduce energy consumption and improve data routes. NORA is an algorithm, which uses local and neighbourhood information to assign a role to each node on the net, whereas NORIA adds a fuzzy logic engine to NORA in order to improve this assignment. These algorithms are far from being trivial, and, therefore, there is a clear need for the use of formal methods to check their correctness and performance, prior to their deployment in a real environment. To this end, this paper presents a neat and rigorous study of both algorithms, and, for the sake of completeness, we study and compare also both with a well-known routing protocol: Tree Routing. Finally, Coloured Petri Nets (CPNs) have been chosen as an appropriate modelling language, using the well-known tool, CPNTools, to conduct our experiments.

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Research Article Mon, 1 Sep 2014 00:00:00 +0300
Behavioral and Temporal Rule Checking for Gaussian Random Process – a Kalman Filter Example https://lib.jucs.org/article/23880/ JUCS - Journal of Universal Computer Science 19(15): 2198-2206

DOI: 10.3217/jucs-019-15-2198

Authors: Doron Drusinsky

Abstract: This paper describes a behavioral and temporal pattern detection technique for state-space systems whose state is a random variable such as the state estimated using a Kalman filter. Our novel behavioral and temporal pattern detection technique uses diagrammatic, intuitive, yet formal specifications based on a dialect of the UML of the kind used to monitor or formally verify the correctness of deterministic systems. Combining these formal specifications with a special code generator, extends the deterministic pattern detection technique to the domain of stochastic processes. We demonstrate the technique using a Ballistic trajectory Kalman filter tracking example in which a pattern-rule of interest is not flagged when observing the sequence of mean track position values but is flagged with a reasonable probability using the proposed technique.

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Research Article Sun, 1 Sep 2013 00:00:00 +0300
The Riesz Representation Operator on the Dual of C[0; 1] is Computable https://lib.jucs.org/article/23243/ JUCS - Journal of Universal Computer Science 19(6): 750-770

DOI: 10.3217/jucs-019-06-0750

Authors: Tahereh Jafarikhah, Klaus Weihrauch

Abstract: By the Riesz representation theorem, for every linear functional F : C[0; 1] → ℝ there is a function g : [0; 1] → ℝ of bounded variation such that A computable version is proved in [Lu and Weihrauch(2007)]: a function g can be computed from F and its norm, and F can be computed from g and an upper bound of its total variation. In this article we present a much more transparent proof. We first give a new proof of the classical theorem from which we then can derive the computable version easily. As in [Lu and Weihrauch(2007)] we use the framework of TTE, the representation approach for computable analysis, which allows to define natural concepts of computability for the operators under consideration.

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Research Article Thu, 28 Mar 2013 00:00:00 +0200
Investigations on a Pedagogical Calculus of Constructions https://lib.jucs.org/article/23241/ JUCS - Journal of Universal Computer Science 19(6): 729-749

DOI: 10.3217/jucs-019-06-0729

Authors: Loïc Colson, Vincent Demange

Abstract: In the last few years appeared pedagogical propositional natural deduction systems. In these systems one must satisfy the pedagogical constraint: the user must give an example of any introduced notion. In formal terms, for instance in the propositional case, the main modification is that we replace the usual rule (hyp) by the rule (p-hyp) where σ denotes a substitution which replaces variables of Γ with an example. This substitution σ is called the motivation of Γ. First we expose the reasons of such a constraint and properties of these "pedagogical" calculi: the absence of negation at logical side, and the "usefulness" feature of terms at computational side (through the Curry-Howard correspondence). Then we construct a simple pedagogical restriction of the calculus of constructions (CC) called CCr. We establish logical limitations of this system, and compare its computational expressiveness to Gödel system T. Finally, guided by the logical limitations of CCr, we give a formal and general definition of a pedagogical calculus of constructions.

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Research Article Thu, 28 Mar 2013 00:00:00 +0200
Controlled Pure Grammar Systems https://lib.jucs.org/article/23847/ JUCS - Journal of Universal Computer Science 18(14): 2024-2040

DOI: 10.3217/jucs-018-14-2024

Authors: Alexander Meduna, Petr Zemek

Abstract: This paper discusses grammar systems that have only terminals, work in the leftmost way, and generate their languages under the regulation by control languages over rule labels. It establishes three results concerning their generative power. First, without any control languages, these systems are not even able to generate all context-free languages. Second, with regular control languages, these systems, having no more than two components, characterize the family of recursively enumerable languages. Finally, with control languages that are themselves generated by regularcontrolled context-free grammars, these systems over unary alphabets generate nothing but regular languages. In its introductory section, the paper gives a motivation for introducing these systems, and in the concluding section, it formulates several open problems.

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Research Article Sat, 28 Jul 2012 00:00:00 +0300
Behavioral and Temporal Pattern Detection within Financial Data with Hidden Information https://lib.jucs.org/article/23844/ JUCS - Journal of Universal Computer Science 18(14): 1950-1966

DOI: 10.3217/jucs-018-14-1950

Authors: Doron Drusinsky

Abstract: This paper describes a technique for behavioral and temporal pattern detection within financial data, such as credit card and bank account data, where the required information is only partially visible. Typically, transaction amount, transaction date, merchant name and type, and location of transaction are all visible data items, i.e., they are readily available in the financial institutions database. In contrast, the transaction status as a business transaction (using a personal card), a personal transaction, an investment related transaction, or perhaps a suspicious transaction, is information not explicitly available in the database. Our behavioral pattern detection technique combines well-known Hidden Markov Model (HMM) techniques for learning and subsequent identification of hidden artifacts, with run-time pattern detection of probabilistic UML-based formal specifications. The proposed approach entails a process in which the end-user first develops his or her deterministic patterns, s/he then identifies hidden artifacts in those patterns. Those artifacts induce the state set of the identifying HMM, whose remaining parameters are learned using standard frequency analysis techniques. In the run-time pattern detection phase, the system emits visible information, used by the HMM to deduce invisible information, and sequences thereof; both types of information are then used by a probabilistic pattern detector to monitor the pattern.

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Research Article Sat, 28 Jul 2012 00:00:00 +0300
A Novel Membrane Algorithm Based on Particle Swarm Optimization for Solving Broadcasting Problems https://lib.jucs.org/article/23797/ JUCS - Journal of Universal Computer Science 18(13): 1821-1841

DOI: 10.3217/jucs-018-13-1821

Authors: Gexiang Zhang, Fen Zhou, Xiaoli Huang, Jixiang Cheng, Marian Gheorghe, Florentin Ipate, Raluca Lefticaru

Abstract: This paper presents the application of membrane algorithms to broadcasting problems, which are regarded as NP-hard combinatorial optimization problems. A membrane algorithm, called HPSOPS, is proposed by appropriately combining membrane systems and a hybrid particle swarm optimization with wavelet mutation (HPSOWM). HPSOPS is designed with the hierarchical membrane structure and transformation/communication-like rules of membrane systems, the representation of individuals and the evolutionary mechanism of HPSOWM. Experimental results from various broadcasting problems show that HPSOPS performs better than its counterpart HPSOWM and genetic algorithms reported in the literature, in terms of search capability, efficiency, solution stability and precision.

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Research Article Sun, 1 Jul 2012 00:00:00 +0300
P Systems with Shuffle Operation and Catalytic-Like Rules https://lib.jucs.org/article/23794/ JUCS - Journal of Universal Computer Science 18(13): 1782-1801

DOI: 10.3217/jucs-018-13-1782

Authors: Yunyun Niu, Jinbang Xu, K. G. Subramanian, Rosni Abdullah

Abstract: Shuffle operation on trajectories is useful in modeling parallel composition of wordsand languages. In this work, a new class of P systems with shuffle operation and catalytic-like rules is presented. Such a system has a membrane structure, where language-objects and shuffle-operation rules are placed in its regions. It can be used as a language generator. In this study, we propose a variant P system with shuffle operation on string-language objects. Some comparisonresults are obtained, which show that the power of shuffle operation is enlarged in the framework of P systems. Moreover, string-language objects are extended to array-language objects, and an-other variant P system with shuffle operation on picture-language objects is introduced. We also illustrate how to generate picture languages by using this kind of devices.

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Research Article Sun, 1 Jul 2012 00:00:00 +0300
Descriptional Complexity of Ambiguity in Symmetric Difference NFAs https://lib.jucs.org/article/29941/ JUCS - Journal of Universal Computer Science 17(6): 874-890

DOI: 10.3217/jucs-017-06-0874

Authors: Lynette van Zijl, Jaco Geldenhuys

Abstract: We investigate ambiguity for symmetric difference nondeterministic finite automata. We show the existence of unambiguous, finitely ambiguous, polynomially ambiguous and exponentially ambiguous symmetric difference nondeterministic finite automata. We show that, for each of these classes, there is a family of n-state nondeterministic finite automata such that the smallest equivalent deterministic finite automata have O(2n) states.

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Research Article Mon, 28 Mar 2011 00:00:00 +0300
Nondeterministic Query Algorithms https://lib.jucs.org/article/29940/ JUCS - Journal of Universal Computer Science 17(6): 859-873

DOI: 10.3217/jucs-017-06-0859

Authors: Alina Vasilieva, Rūsiņš Freivalds

Abstract: Query algorithms are used to compute Boolean functions. The definition of the function is known, but input is hidden in a black box. The aim is to compute the function value using as few queries to the black box as possible. As in other computational models, different kinds of query algorithms are possible: deterministic, probabilistic, as well as nondeterministic. In this paper, we present a new alternative definition of nondeterministic query algorithms and study algorithm complexity in this model. We demonstrate the power of our model with an example of computing the Fano plane Boolean function. We show that for this function the difference between deterministic and nondeterministic query complexity is 7N versus O(3N).

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Research Article Mon, 28 Mar 2011 00:00:00 +0300
XML Database Transformations https://lib.jucs.org/article/29847/ JUCS - Journal of Universal Computer Science 16(20): 3043-3072

DOI: 10.3217/jucs-016-20-3043

Authors: Klaus-Dieter Schewe, Qing Wang

Abstract: Database transformations provide a unifying umbrella for queries and updates. In general, they can be characterised by five postulates, which constitute the database analogue of Gurevich's sequential ASM thesis. Among these postulates the background postulate supposedly captures the particularities of data models and schemata. For the characterisation of XML database transformations the natural first step is therefore to define the appropriate tree-based backgrounds, which draw on hereditarily finite trees, tree algebra operations, and extended document type definitions. This defines a computational model for XML database transformation using a variant of Abstract State Machines. Then the incorporation of weak monadic second-order logic provides an alternative computational model called XML machines. The main result is that these two computational models for XML database transformations are equivalent.

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Research Article Mon, 1 Nov 2010 00:00:00 +0200
A Note on Closed Subsets in Quasi-zero-dimensional Qcb-spaces https://lib.jucs.org/article/29807/ JUCS - Journal of Universal Computer Science 16(18): 2711-2732

DOI: 10.3217/jucs-016-18-2711

Authors: Matthias Schröder

Abstract: We introduce the notion of quasi-zero-dimensionality as a substitute for the notion of zero-dimensionality, motivated by the fact that the latter behaves badly in the realm of qcb-spaces. We prove that the category QZ of quasi-zero-dimensional qcblt;sub>0lt;/sub>-spaces is cartesian closed. Prominent examples of spaces in QZ are the spaces of the Kleene-Kreisel continuous functionals equipped with the respective sequential topology. Moreover, we characterise some types of closed subsets of QZ-spaces in terms of their ability to allow extendability of continuous functions. These results are related to a problem in Computable Analysis.

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Research Article Tue, 28 Sep 2010 00:00:00 +0300
Compositional Semantics of Dataflow Networks with Query-Driven Communication of Exact Values https://lib.jucs.org/article/29801/ JUCS - Journal of Universal Computer Science 16(18): 2629-2656

DOI: 10.3217/jucs-016-18-2629

Authors: Michal Konečný, Amin Farjudian

Abstract: We develop and study the concept of dataflow process networks as used for exampleby Kahn to suit exact computation over data types related to real numbers, such as continuous functions and geometrical solids. Furthermore, we consider communicating these exact objectsamong processes using protocols of a query-answer nature as introduced in our earlier work. This enables processes to provide valid approximations with certain accuracy and focusing on certainlocality as demanded by the receiving processes through queries. We define domain-theoretical denotational semantics of our networks in two ways: (1) directly, i. e. by viewing the whole network as a composite process and applying the process semantics introduced in our earlier work; and (2) compositionally, i. e. by a fixed-point construction similarto that used by Kahn from the denotational semantics of individual processes in the network. The direct semantics closely corresponds to the operational semantics of the network (i. e. it iscorrect) but very difficult to study for concrete networks. The compositional semantics enablescompositional analysis of concrete networks, assuming it is correct. We prove that the compositional semantics is a safe approximation of the direct semantics. Wealso provide a method that can be used in many cases to establish that the two semantics fully coincide, i. e. safety is not achieved through inactivity or meaningless answers. The results are extended to cover recursively-defined infinite networks as well as nested finitenetworks. A robust prototype implementation of our model is available.

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Research Article Tue, 28 Sep 2010 00:00:00 +0300
Semantics of Query-Driven Communication of Exact Values https://lib.jucs.org/article/29800/ JUCS - Journal of Universal Computer Science 16(18): 2597-2628

DOI: 10.3217/jucs-016-18-2597

Authors: Michal Konečný, Amin Farjudian

Abstract: We address the question of how to communicate among distributed processes valuessuch as real numbers, continuous functions and geometrical solids with arbitrary precision, yet efficiently. We extend the established concept of lazy communication using streams of approximants by introducing explicit queries. We formalise this approach using protocols of a query-answer nature. Such protocols enable processes to provide valid approximations with certain accuracy and focusing on certain locality as demanded by the receiving processes through queries. A lattice-theoretic denotational semantics of channel and process behaviour is developed. Thequery space is modelled as a continuous lattice in which the top element denotes the query demanding all the information, whereas other elements denote queries demanding partial and/or local information. Answers are interpreted as elements of lattices constructed over suitable domains of approximations to the exact objects. An unanswered query is treated as an error anddenoted using the top element. The major novel characteristic of our semantic model is that it reflects the dependency of answerson queries. This enables the definition and analysis of an appropriate concept of convergence rate, by assigning an effort indicator to each query and a measure of information content to eachanswer. Thus we capture not only what function a process computes, but also how a process transforms the convergence rates from its inputs to its outputs. In future work these indicatorscan be used to capture further computational complexity measures. A robust prototype implementation of our model is available.

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Research Article Tue, 28 Sep 2010 00:00:00 +0300
The Separation of Relativized Versions of P and DNP for the Ring of the Reals https://lib.jucs.org/article/29798/ JUCS - Journal of Universal Computer Science 16(18): 2563-2568

DOI: 10.3217/jucs-016-18-2563

Authors: Christine Gaßner

Abstract: We consider the uniform BSS model of computation where the machines can perform additions, multiplications, and tests of the form x ≥ 0. The oracle machines can also check whether a tuple of real numbers belongs to a given oracle set or not. We present oracle sets containing positive integers and pairs of numbers, respectively, such that the classes P and DNP relative to these oracles are not equal. The first set is constructed by diagonalization techniques and the second one is derived from the Knapsack Problem.

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Research Article Tue, 28 Sep 2010 00:00:00 +0300
PICTAC: A Model for Perceiving Touch Interaction through Tagging Context https://lib.jucs.org/article/29714/ JUCS - Journal of Universal Computer Science 16(12): 1577-1591

DOI: 10.3217/jucs-016-12-1577

Authors: Gabriel Chavira, José Bravo, Salvador Nava-Díaz, Julio Rolón

Abstract: A natural interface is one of three key technologies of Ambient Intelligence (AmI); one of its main objectives is to minimize the user's interactive effort, which is the difficulty level that depends on the diversity and quantity of devices that surround people in existing environments. The worldwide penetration of mobile phones at present makes mobile phones excellent devices for delivering new services to users without requiring learning effort. An NFC-enabled mobile phone will allow a user to demand and obtain services by touching its different elements in a given smart environment. In this paper, we present a proposal in which we analyze the scope of touch interaction and develop a perceived touch interaction through tagging context (PICTAC) model.

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Research Article Mon, 28 Jun 2010 00:00:00 +0300
Ordered Catenation Closures and Decompositions of Languages Related to a Language of Derick Wood https://lib.jucs.org/article/29641/ JUCS - Journal of Universal Computer Science 16(5): 821-832

DOI: 10.3217/jucs-016-05-0821

Authors: Arto Salomaa

Abstract: We investigate the problem of decomposing a language into a catenation of nontrivial languages, none of which can be decomposed further. In many cases this leads to the operation of an ordered catenation closure, introduced in this paper. We study properties of this operation, as well as its iterations. Special emphasis is on laid on ordered catenation closures of finite languages. It is also shown that if an infinite language is a code or a length code, then its ordered catenation closure does not possess a finite decomposition of indecomposable factors.

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Research Article Mon, 1 Mar 2010 00:00:00 +0200
On Succinct Representations of Textured Surfaces by Weighted Finite Automata https://lib.jucs.org/article/29620/ JUCS - Journal of Universal Computer Science 16(5): 586-603

DOI: 10.3217/jucs-016-05-0586

Authors: Jürgen Albert, German Tischler

Abstract: Generalized finite automata with weights for states and transitions have been successfully applied to image generation for more than a decade now. Bilevel images (black and white), grayscale- or color-images and even video sequences can be effectively coded as weighted finite automata. Since each state represents a subimage within those automata the weighted transitions can exploit self-similarities for image compression. These "fractal" approaches yield remarkable results in comparison to the well-known standard JPEG- or MPEG-encodings and frequently provide advantages for images with strong contrasts. Here we will study the combination of these highly effective compression techniques with a generalization of weighted finite automata to higher dimensions, which establish d-dimensional relations between resultsets of ordinary weighted automata. For the applications we will restrict ourselves to three-dimensional Bezier spline-patches and to grayscale images as textures.

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Research Article Mon, 1 Mar 2010 00:00:00 +0200
A Hammerstein-Wiener Recurrent Neural Network with Frequency-Domain Eigensystem Realization Algorithm for Unknown System Identification https://lib.jucs.org/article/29499/ JUCS - Journal of Universal Computer Science 15(13): 2547-2565

DOI: 10.3217/jucs-015-13-2547

Authors: Yi-Chung Chen, Jeen-Shing Wang

Abstract: This paper presents a Hammerstein-Wiener recurrent neural network (HWRNN) with a systematic identification algorithm for identifying unknown dynamic nonlinear systems. The proposed HWRNN resembles the conventional Hammerstein-Wiener model that consists of a linear dynamic subsystem that is sandwiched in between two nonlinear static subsystems. The static nonlinear parts are constituted by feedforward neural networks with nonlinear functions and the dynamic linear part is approximated by a recurrent network with linear activation functions. The novelties of our network include: 1) the structure of the proposed recurrent neural network can be mapped into a state-space equation; and 2) the state-space equation can be used to analyze the characteristics of the identified network. To efficiently identify an unknown system from its input-output measurements, we have developed a systematic identification algorithm that consists of parameter initialization and online learning procedures. Computer simulations and comparisons with some existing models have been conducted to demonstrate the effectiveness of the proposed network and its identification algorithm.

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Research Article Wed, 1 Jul 2009 00:00:00 +0300
Elementary Computable Topology https://lib.jucs.org/article/29394/ JUCS - Journal of Universal Computer Science 15(6): 1381-1422

DOI: 10.3217/jucs-015-06-1381

Authors: Klaus Weihrauch, Tanja Grubba

Abstract: We revise and extend the foundation of computable topology in the framework of Type-2 theory of effectivity, TTE, where continuity and computability on finite and infinite sequences of symbols are defined canonically and transferred to abstract sets by means of notations and representations. We start from a computable topological space, which is a T0-space with a notation of a base such that intersection is computable, and define a number of multi-representations of the points and of the open, the closed and the compact sets and study their properties and relations. We study computability of boolean operations. By merely requiring "provability" of suitable relations (element, non-empty intersection, subset) we characterize in turn computability on the points, the open sets (!), computability on the open sets, computability on the closed sets, the compact sets(!), and computability on the compact sets. We study modifications of the definition of a computable topological space that do not change the derived computability concepts. We study subspaces and products and compare a number of representations of the space of partial continuous functions. Since we are operating mainly with the base elements, which can be considered as regions for points ("pointless topology"), we study to which extent these regions can be filled with points (completions). We conclude with some simple applications including Dini's Theorem as an example.

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Research Article Sat, 28 Mar 2009 00:00:00 +0200
An Effective Tietze-Urysohn Theorem for QCB-Spaces https://lib.jucs.org/article/29389/ JUCS - Journal of Universal Computer Science 15(6): 1317-1336

DOI: 10.3217/jucs-015-06-1317

Authors: Matthias Schröder

Abstract: The Tietze-Urysohn Theorem states that every continuous real-valued function defined on a closed subspace of a normal space can be extended to a continuous function on the whole space. We prove an effective version of this theorem in the Type Two Model of Effectivity (TTE). Moreover, we introduce for qcb-spaces a slightly weaker notion of normality than the classical one and show that this property suffices to establish an Extension Theorem for continuous functions defined on functionally closed subspaces. Qcb-spaces are known to form an important subcategory of the category Top of topological spaces. QCB is cartesian closed in contrast to Top.

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Research Article Sat, 28 Mar 2009 00:00:00 +0200
Representing Measurement Results https://lib.jucs.org/article/29386/ JUCS - Journal of Universal Computer Science 15(6): 1280-1300

DOI: 10.3217/jucs-015-06-1280

Authors: Arno Pauly

Abstract: To gain insight into the relationship between physical theories and computation, we examine the link between measurement devices and computers in the framework of TTE. Starting from a formal definition of a measurement procedure, different approaches to associate a representation with a measurement procedure are studied, and an equivalence class of representations suitable for representing the results of a measurement is defined for each measurement procedure.

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Research Article Sat, 28 Mar 2009 00:00:00 +0200
Oracles and Relativizations of the P =? NP Question for Several Structures https://lib.jucs.org/article/29381/ JUCS - Journal of Universal Computer Science 15(6): 1186-1205

DOI: 10.3217/jucs-015-06-1186

Authors: Christine Gaßner

Abstract: We consider the uniform model of computation over any structure with two constants. For several structures, we construct oracles which imply that the relativized versions of P and NP are equal or are not equal. We construct universal oracles which imply the equality of the relativized versions of P and NP and we show that we lose the possibility to define these oracles recursively if we try to compress their elements to tuples of fixed length. Moreover we give new oracles for the BSS model in order to separate the classes P and NP relative to these oracles.

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Research Article Sat, 28 Mar 2009 00:00:00 +0200
Effective Computability of Solutions of Differential Inclusions The Ten Thousand Monkeys Approach https://lib.jucs.org/article/29379/ JUCS - Journal of Universal Computer Science 15(6): 1162-1185

DOI: 10.3217/jucs-015-06-1162

Authors: Pieter Collins, Daniel Graça

Abstract: In this paper we consider the computability of the solution of the initialvalue problem for differential equations and for differential inclusions with semicontinuous right-hand side. We present algorithms for the computation of the solution using the "ten thousand monkeys" approach, in which we generate all possible solution tubes, and then check which are valid. In this way, we show that the solution of a locally Lipschitz differential equation is computable even if the function is not effectively locally Lipschitz, and recover a result of Ruohonen, in which it is shown that if the solution is unique, then it is computable. We give an example of a computable locally Lipschitz function which is not effectively locally Lipschitz. We also show that the solutions of a convex-valued upper-semicontinuous differential inclusion are upper-semicomputable, and the solutions of a lower-semicontinuous one-sided Lipschitz differential inclusion are lower-semicomputable.

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Research Article Sat, 28 Mar 2009 00:00:00 +0200
Notions of Probabilistic Computability on Represented Spaces https://lib.jucs.org/article/29014/ JUCS - Journal of Universal Computer Science 14(6): 956-995

DOI: 10.3217/jucs-014-06-0956

Authors: Volker Bosserhoff

Abstract: We define and compare several probabilistic notions of computability for mappings from represented spaces (that are equipped with a measure or outer measure) into computable metric spaces. We thereby generalize definitions by [Ko 1991] and Parker (see [Parker 2003, Parker 2005, Parker 2006]), and furthermore introduce the new notion of computability in the mean. Some results employ a notion of computable measure that originates in definitions by [Weihrauch 1999] and [Schröder 2007]. In the spirit of the well-known Representation Theorem (see [Weihrauch 2000]), we establish dependencies between the probabilistic computability notions and classical properties of mappings. We furthermore present various results on the computability of vector-valued integration, composition of mappings, and images of measures. Finally, we discuss certain measurability issues arising in connection with our definitions.

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Research Article Fri, 28 Mar 2008 00:00:00 +0200
Computable Riesz Representation for Locally Compact Hausdorff Spaces https://lib.jucs.org/article/29006/ JUCS - Journal of Universal Computer Science 14(6): 845-860

DOI: 10.3217/jucs-014-06-0845

Authors: Hong Lu, Klaus Weihrauch

Abstract: By the Riesz Representation Theorem for locally compact Hausdorff spaces, for every positive linear functional I on K(X) there is a measure μ such that I(f) =∫ f dμ where K(X) is the set of continuous real functions with compact support on the locally compact Hausdorff space X. In this article we prove a uniformly computable version of this theorem for computably locally compact computable Hausdorff spaces X. We introduce a representation of the positive linear functionals I on K(X) and a representation of the Borel measures on X and prove that for every such functional I a measure μ can be computed and vice versa such that I(f) = ∫ f dμ.

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Research Article Fri, 28 Mar 2008 00:00:00 +0200
Spiking Neural P Systems with Astrocyte-Like Control https://lib.jucs.org/article/28897/ JUCS - Journal of Universal Computer Science 13(11): 1707-1721

DOI: 10.3217/jucs-013-11-1707

Authors: Gheorghe Păun

Abstract: Spiking neural P systems are computing models inspired from the way the neurons communicate by means of spikes, electrical impulses of identical shapes. In this note we consider a further important ingredient related to brain functioning, the astrocyte cells which fed neurons with nutrients, implicitly controlling their functioning. Specifically, we introduce in our models only one feature of astrocytes, formulated as a control of spikes traffic along axons. A normal form is proved (for systems without forgetting rules) and decidability issues are discussed.

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Research Article Wed, 28 Nov 2007 00:00:00 +0200
Accepting Networks of Evolutionary Processors with Filtered Connections https://lib.jucs.org/article/28884/ JUCS - Journal of Universal Computer Science 13(11): 1598-1614

DOI: 10.3217/jucs-013-11-1598

Authors: Cezara Drăgoi, Florin Manea, Victor Mitrana

Abstract: In this paper we simplify a recent model of computation considered in [Margenstern et al. 2005], namely accepting network of evolutionary processors, by moving the filters from the nodes to the edges. Each edge is viewed as a two-way channel such that input and output filters, respectively, of the two nodes connected by the edge coincide. Thus, the possibility of controlling the computation in such networks seems to be diminished. In spite of this observation these simplified networks have the same computational power as accepting networks of evolutionary processors, that is they are computationally complete. As a consequence, we propose characterizations of two complexity classes, namely NP and PSPACE, in terms of accepting networks of evolutionary processors with filtered connections.

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Research Article Wed, 28 Nov 2007 00:00:00 +0200
Equivalent Transformations of Automata by Using Behavioural Automata https://lib.jucs.org/article/28880/ JUCS - Journal of Universal Computer Science 13(11): 1540-1549

DOI: 10.3217/jucs-013-11-1540

Authors: Gabriel Ciobanu, Sergiu Rudeanu

Abstract: This paper uses category theory to emphasize the relationships between Mealy, Moore and Rabin-Scott automata, and the behavioural automata are used as a unifying framework. Some of the known links between Mealy, Moore and RabinScott automata are translated into isomorphisms of categories, and we also show how behavioural automata connect to these automata. Considering the distinction between final and sequential behaviours of an automaton, we define a sequential version of Mealy automata and study its relationship to behavioural automata.

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Research Article Wed, 28 Nov 2007 00:00:00 +0200
Pedagogical Natural Deduction Systems: the Propositional Case https://lib.jucs.org/article/28861/ JUCS - Journal of Universal Computer Science 13(10): 1396-1410

DOI: 10.3217/jucs-013-10-1396

Authors: Loïc Colson, David Michel

Abstract: This paper introduces the notion of pedagogical natural deduction systems, which are natural deduction systems with the following additional constraint: all hypotheses made in a proof must be motivated by some example. It is established that such systems are negationless. The expressive power of the pedagogical version of some propositional calculi are studied.

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Research Article Sun, 28 Oct 2007 00:00:00 +0300
Programming through Spreadsheets and Tabular Abstractions https://lib.jucs.org/article/28807/ JUCS - Journal of Universal Computer Science 13(6): 806-816

DOI: 10.3217/jucs-013-06-0806

Authors: Carlos Henrique Q. Forster

Abstract: The spreadsheet metaphor has, over the years, proved itself valuable for the definition and use of computations by non-programmers. However, the computation model adopted in commercial spreadsheets is still limited to non-recursive computations and lacks abstraction mechanisms that would provide modularization and better reuse (beyond copy and paste). We investigate these problems by identifying a minimal set of requirements for recursive computations, designing a spreadsheet-based language with an abstraction definition mechanism, prototyping an interpreter and evaluating it with examples.

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Research Article Thu, 28 Jun 2007 00:00:00 +0300
Time-varying H Systems Revisited https://lib.jucs.org/article/28693/ JUCS - Journal of Universal Computer Science 12(10): 1455-1463

DOI: 10.3217/jucs-012-10-1455

Authors: Remco Loos

Abstract: We cast a new look on time-varying distributed H systems. In their original definition, where only new strings are passed to the next component, this language definition in itself is already enough to obtain computational completeness. Here, we consider two types of time-varying H systems with weaker language definitions, based on the usual definition of splicing systems: The next generation of strings consists of the union of all existing strings and the newly created strings. We show that if all strings, both old and new, are passed to the next component these systems are regular in power. If however, the new strings pass to the next component and the existing ones remain accessible to the current one, we prove that systems with 4 components are already computationally complete.

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Research Article Sat, 28 Oct 2006 00:00:00 +0300
Membrane Computing and Graphical Operating Systems https://lib.jucs.org/article/28679/ JUCS - Journal of Universal Computer Science 12(9): 1312-1331

DOI: 10.3217/jucs-012-09-1312

Authors: Benedek Nagy, László Szegedi

Abstract: In this paper a comparison is provided between the membrane computing systems and the graphical interfaces of operating systems. A membrane computing system is a computing model using massive parallelism inspired by the functioning of living cells. The graphical schemes of these computing devices look like the windows of a graphical operating system representing programs running parallel on the computer. Both similarities and differences of membrane-systems and graphical operating systems are detailed as well as some possible simulation methods.

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Research Article Thu, 28 Sep 2006 00:00:00 +0300
Defining Atomic Composition in UML Behavioral Diagrams https://lib.jucs.org/article/28643/ JUCS - Journal of Universal Computer Science 12(7): 958-979

DOI: 10.3217/jucs-012-07-0958

Authors: Júlio Machado, Paulo Menezes

Abstract: UML may be used to describe both the structure and behavior of objectoriented systems using a combination of notations. For the modeling of the dynamic behavior, a number of different models are offered such as interaction, state and activity diagrams. Although compositional techniques for modeling computational processes demand means of composing elements both in non-atomic or atomic ways, UML seems to lack compositional constructs for defining atomic composites. We discuss proper extensions for diagrams that are able to cope with the concept of atomic composition as the basic element for describing transactions (in our settings the term "transaction" denotes a certain operation of a system that might be atomically composed by many, possibly concurrent, operations). Atomic compositions are then formally defined through a special morphism between automata in a domain called Nonsequential Automata.

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Research Article Fri, 28 Jul 2006 00:00:00 +0300
Progress in Quantum Computational Cryptography https://lib.jucs.org/article/28626/ JUCS - Journal of Universal Computer Science 12(6): 691-709

DOI: 10.3217/jucs-012-06-0691

Authors: Akinori Kawachi, Takeshi Koshiba

Abstract: Shor's algorithms for the integer factorization and the discrete logarithm problems can be regarded as a negative effect of the quantum mechanism on publickey cryptography. From the computational point of view, his algorithms illustrate that quantum computation could be more powerful. It is natural to consider that the power of quantum computation could be exploited to withstand even quantum adversaries. Over the last decade, quantum cryptography has been discussed and developed even from the computational complexity-theoretic point of view. In this paper, we will survey what has been studied in quantum computational cryptography.

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Research Article Wed, 28 Jun 2006 00:00:00 +0300
On-line Monitoring of Metric Temporal Logic with Time-Series Constraints Using Alternating Finite Automata https://lib.jucs.org/article/28613/ JUCS - Journal of Universal Computer Science 12(5): 482-498

DOI: 10.3217/jucs-012-05-0482

Authors: Doron Drusinsky

Abstract: In this paper we describe a technique for monitoring and checking temporal logic assertions augmented with real-time and time-series constraints, or Metric Temporal Logic Series (MTLS). The method is based on Remote Execution and Monitoring (REM) of temporal logic assertions. We describe the syntax and semantics of MTLS and a monitoring technique based on alternating finite automata that is efficient for a large set of frequently used formulae and is also an on-line technique. We investigate the run-time data-structure size for several interesting assertions taken from the Kansas State specification patterns.

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Research Article Sun, 28 May 2006 00:00:00 +0300
Visualization Services in a Conference Context: An Approach by RFID Technology https://lib.jucs.org/article/28583/ JUCS - Journal of Universal Computer Science 12(3): 270-283

DOI: 10.3217/jucs-012-03-0270

Authors: José Bravo, Ramón Hervás, Inocente Sánchez, Gabriel Chavira, Salvador Nava

Abstract: Ambient Intelligent (AmI) vision is a new concept materialized by the Six Framework Program of the European Community. It involves three key technologies: Ubiquitous Computing, Ubiquitous Communications and Natural Interfaces. With the increase in context aware applications it is important to keep these technologies in mind. In this paper we present a context aware application in a conference site based on the identification process using RFID. Furthermore the highlights of this proposal are based on the "ws" concepts. Three environments are modelled applying the "who" to the "when" and "where" to reach the "what". In this sense certain services are offered to the conference attendees, some of which are characteristics of this technology and others are the result of a context aware application, the visualization services named "Mosaics of Information".

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Research Article Tue, 28 Mar 2006 00:00:00 +0300
A Structure Causality Relation for Liveness Characterisation in Petri Nets https://lib.jucs.org/article/28576/ JUCS - Journal of Universal Computer Science 12(2): 214-232

DOI: 10.3217/jucs-012-02-0214

Authors: Belhassen Zouari

Abstract: Characterising liveness using a structure based approach is a key issue in theory of Petri nets. In this paper, we introduce a structure causality relation from which a topological characterisation of liveness in Petri nets is defined. This characterisation relies on a controllability property of siphons and allows to determine the borders of the largest abstract class of Petri nets for which equivalence between liveness and deadlock-freeness holds. Hence, interesting subclasses of P/T systems, for which membership can be easily determined, are presented. Moreover, this paper resumes, from a new point of view, similar results related to this issue and, provides a unified interpretation of the causes of the non-equivalence between liveness and deadlock-freeness.

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Research Article Tue, 28 Feb 2006 00:00:00 +0200
Hausdorff Measure and Lukasiewicz Languages https://lib.jucs.org/article/28541/ JUCS - Journal of Universal Computer Science 11(12): 2114-2124

DOI: 10.3217/jucs-011-12-2114

Authors: Ludwig Staiger

Abstract: The paper investigates fixed points and attractors of infinite iterated function systems in Cantor space. By means of the theory of formal languages simple examples of the non-coincidence of fixed point and attractor (closure of the fixed point) are given.

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Research Article Wed, 28 Dec 2005 00:00:00 +0200
Quotient Spaces and Coequalisers in Formal Topology https://lib.jucs.org/article/28527/ JUCS - Journal of Universal Computer Science 11(12): 1996-2007

DOI: 10.3217/jucs-011-12-1996

Authors: Erik Palmgren

Abstract: We give a construction of coequalisers in formal topology, a predicative version of locale theory. This allows for construction of quotient spaces and identification spaces in constructive topology.

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Research Article Wed, 28 Dec 2005 00:00:00 +0200
Formal Topology and Constructive Mathematics: the Gelfand and Stone-Yosida Representation Theorems https://lib.jucs.org/article/28520/ JUCS - Journal of Universal Computer Science 11(12): 1932-1944

DOI: 10.3217/jucs-011-12-1932

Authors: Thierry Coquand, Bas Spitters

Abstract: We present a constructive proof of the Stone-Yosida representation theorem for Riesz spaces motivated by considerations from formal topology. This theorem is used to derive a representation theorem for f-algebras. In turn, this theorem implies the Gelfand representation theorem for C*-algebras of operators on Hilbert spaces as formulated by Bishop and Bridges. Our proof is shorter, clearer, and we avoid the use of approximate eigenvalues.

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Research Article Wed, 28 Dec 2005 00:00:00 +0200
Computability of the Spectrum of Self-Adjoint Operators https://lib.jucs.org/article/28515/ JUCS - Journal of Universal Computer Science 11(12): 1884-1900

DOI: 10.3217/jucs-011-12-1884

Authors: Vasco Brattka, Ruth Dillhage

Abstract: Self-adjoint operators and their spectra play a crucial role in analysis and physics. For instance, in quantum physics self-adjoint operators are used to describe measurements and the spectrum represents the set of possible measurement results. Therefore, it is a natural question whether the spectrum of a self-adjoint operator can be computed from a description of the operator. We prove that given a "program" of the operator one can obtain positive information on the spectrum as a compact set in the sense that a dense subset of the spectrum can be enumerated (or equivalently: its distance function can be computed from above) and a bound on the set can be computed. This generalizes some non-uniform results obtained by Pour-El and Richards, which imply that the spectrum of any computable self-adjoint operator is a recursively enumerable compact set. Additionally, we show that the spectrum of compact self-adjoint operators can even be computed in the sense that also negative information is available (i.e. the distance function can be fully computed). Finally, we also discuss computability properties of the resolvent map.

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Research Article Wed, 28 Dec 2005 00:00:00 +0200
The Tiling of the Hyperbolic 4D Space by the 120-cell is Combinatoric https://lib.jucs.org/article/28293/ JUCS - Journal of Universal Computer Science 10(9): 1212-1238

DOI: 10.3217/jucs-010-09-1212

Authors: Maurice Margenstern

Abstract: The splitting method was defined by the author in [Margenstern 2002a], [Margenstern 2002d]. It is at the basis of the notion of combinatoric tilings. As a consequence of this notion, there is a recurrence sequence which allows us to compute the number of tiles which are at a fixed distance from a given tile. A polynomial is attached to the sequence as well as a language which can be used for implementing cellular automata on the tiling. The goal of this paper is to prove that the tiling of hyperbolic 4D space is combinatoric. We give here the corresponding polynomial and, as the first consequence, the language of the splitting is not regular, as it is the case in the tiling of hyperbolic 3D space by rectangular dodecahedra which is also combinatoric.

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Research Article Tue, 28 Sep 2004 00:00:00 +0300
An Efficient Family of P Systems for Packing Items into Bins https://lib.jucs.org/article/28239/ JUCS - Journal of Universal Computer Science 10(5): 650-670

DOI: 10.3217/jucs-010-05-0650

Authors: Mario Pérez-Jiménez, Francisco Romero-Campero

Abstract: In this paper we present an effective solution to the Bin Paching problem using a family of recognizer P systems with active membranes. The analysis of the solution presented here will be done from the point of view of complexity classes. A CLIPS simulator for recognizer P systems is used to describe a session for an instance of Bin Packing, using a P system from the designed family.

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Research Article Fri, 28 May 2004 00:00:00 +0300
P Systems with Active Membranes and Separation Rules https://lib.jucs.org/article/28238/ JUCS - Journal of Universal Computer Science 10(5): 630-649

DOI: 10.3217/jucs-010-05-0630

Authors: Linqiang Pan, Tseren-Onolt Ishdorj

Abstract: The P systems are a class of distributed parallel computing devices of a biochemical type. In this paper, a new definition of separation rules in P systems with active membranes is given. Under the new definition, the efficiency and universality of P systems with active membranes and separation rules instead of division rules are investigated.

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Research Article Fri, 28 May 2004 00:00:00 +0300
A Java Simulator for Membrane Computing https://lib.jucs.org/article/28237/ JUCS - Journal of Universal Computer Science 10(5): 620-629

DOI: 10.3217/jucs-010-05-0620

Authors: Isabel Nepomuceno-Chamorro

Abstract: Membrane Computing is a recent area of Natural Computing, a topic where much work has been done but still much remains to be done. There are some applications which have been developed in imperative languages, like C++, or in declaratives languages, as Prolog, working in the framework of P systems. In this paper, a software tool (called SimCM, from Spanish Simulador de Computacion con Membranas) for handling P systems is presented. The program can simulate basic transition P Systems where dissolution of membranes and priority rules are allowed. The software application is carried out in an imperative and object-oriented language - Java. We choose Java because it is a scalable and distributed language. Working with Java is the first step to cross the border between simulations and a distributed implementation able to capture the parallelism existing in the membrane computing area. This tool is a friendly application which allows us to follow the evolution of a P system easily and in a visual way. The program can be used to move the P system theory closer to the biologist and all the people who wants to learn and understand how this model works.

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Research Article Fri, 28 May 2004 00:00:00 +0300
Simulating the Fredkin Gate with Energy-Based P Systems https://lib.jucs.org/article/28236/ JUCS - Journal of Universal Computer Science 10(5): 600-619

DOI: 10.3217/jucs-010-05-0600

Authors: Alberto Leporati, Claudio Zandron, Giancarlo Mauri

Abstract: Reversibility plays a fundamental role when the possibility to perform computations with minimal energy dissipation is considered. Many papers on reversible computation have appeared in literature, the most famous of which is certainly the work of Bennett on (universal) reversible Turing machines. Here we consider the work of Fredkin and Toffoli on conservative logic, which is a mathematical model that allows to describe computations which reflect some properties of microdynamical laws of physics, such as reversibility and conservation of the internal energy of the physical system used to perform the computations. The model is based upon the Fredkin gate, a reversible and "conservative" (according to a definition given by Fredkin and Toffoli) three-input/three-output boolean gate. In this paper we introduce energy{based P systems as a parallel and distributed model of computation in which the amount of energy manipulated and/or consumed during computations is taken into account. Moreover, we show how energy-based P systems can be used to simulate the Fredkin gate. The proposed P systems that perform the simulations turn out to be themselves reversible and conservative.

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Research Article Fri, 28 May 2004 00:00:00 +0300
Finding the Maximum Element Using P Systems https://lib.jucs.org/article/28232/ JUCS - Journal of Universal Computer Science 10(5): 567-580

DOI: 10.3217/jucs-010-05-0567

Authors: Federico Fontana, Giuditta Franco

Abstract: A nondeterministic, maximally parallel methodology for finding the maximum element in a set of numerical values is presented, suitable for being implemented on P systems. Several algorithms of maximum search are then developed for different types of such systems, namely using priorities, nested membranes and linked transport, and their performances are evaluated accordingly. The proposed solutions are expected to find application inside membrane models devoted to compute algorithmic procedures in which the greatest element in a data set must be found. Dynamic algorithms for DNA sequence alignment are an example of such procedures.

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Research Article Fri, 28 May 2004 00:00:00 +0300
A Note on Complexity Measures for Probabilistic P Systems https://lib.jucs.org/article/28230/ JUCS - Journal of Universal Computer Science 10(5): 559-566

DOI: 10.3217/jucs-010-05-0559

Authors: Andrés Cordón-Franco, Fernando Sancho-Caparrini

Abstract: In this paper we present a first approach to the definition of different entropy measures for probabilistic P systems in order to obtain some quantitative parameters showing how complex the evolution of a P system is. To this end, we define two possible measures, the first one to reflect the entropy of the P system considered as the state space of possible computations, and the second one to reflect the change of the P system as it evolves.

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Research Article Fri, 28 May 2004 00:00:00 +0300
Population P Systems https://lib.jucs.org/article/28224/ JUCS - Journal of Universal Computer Science 10(5): 509-539

DOI: 10.3217/jucs-010-05-0509

Authors: Francesco Bernardini, Marian Gheorghe

Abstract: This paper introduces a notion of population P systems as a class of tissue P systems where the links between the cells can be modified by means of a specific set of bond making rules. As well as this, cell division rules which introduce new cells into the system, cell differentiation rules which change the set of rules that can be used inside of a cell, and cell death rules which remove cells from the system are also considered by introducing a particular notion of population P systems with active cells. The paper mainly reports universality results for the following models: (a) population P systems where cells are restricted to communicate only by means of the environment but never forming any bond, (b) population P systems with bond making rules with restricted communication rules, (c) population P systems possessing only the cell differentiation operation, and (d) population P systems equipped with cell division rules and bond making rules.

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Research Article Fri, 28 May 2004 00:00:00 +0300
Defining a Formal Coalgebraic Semantics for The Rosetta Specification Language https://lib.jucs.org/article/28135/ JUCS - Journal of Universal Computer Science 9(11): 1322-1349

DOI: 10.3217/jucs-009-11-1322

Authors: Cindy Kong, Perry Alexander, Catherine Menon

Abstract: Rosetta is a systems level design language that allows algebraic specification of systems through facets. The usual approach to formally describe a specification is to define an algebra that satisfies the specification. Although it is possible to formally describe Rosetta facets with the use of algebras, we choose to use the dual of algebra, i.e. coalgebra, to do so. Coalgebras are particularly suited for describing state-based systems. This makes formally defining state-based Rosetta quite straightforward. For non-state-based Rosetta, the formalization is not as direct, but can still be done with coalgebras by focusing on the behaviors of systems specified. We use denotational semantics to map Rosetta syntactic constructs into a language understood by the coalgebras.

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Research Article Fri, 28 Nov 2003 00:00:00 +0200
Fibonacci Type Coding for the Regular Rectangular Tilings of the Hyperbolic Plane https://lib.jucs.org/article/28019/ JUCS - Journal of Universal Computer Science 9(5): 398-422

DOI: 10.3217/jucs-009-05-0398

Authors: Maurice Margenstern

Abstract: The study of cellular automata (CA) on tilings of hyperbolic plane was initiated in [6]. Appropriate tools were developed which allow us to produce linear algorithms to implement cellular automata on the tiling of the hyperbolic plane with the regular rectangular pentagons, [8, 10]. In this paper we modify and improve these tools, generalise the algorithms and develop them for tilings of the hyperbolic plane with regular rectangular s-gons for s 5. For this purpose a combinatorial structure of these tilings is studied.

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Research Article Wed, 28 May 2003 00:00:00 +0300
A Multiply Hierarchical Automaton Semantics for the IWIM Coordination Model https://lib.jucs.org/article/27925/ JUCS - Journal of Universal Computer Science 9(1): 2-33

DOI: 10.3217/jucs-009-01-0002

Authors: Richard Banach, Farhad Arbab, George Papadopoulos, John R. W. Glauert

Abstract: The drawbacks of programming coordination activities directly within the applications software that needs them are briefly reviewed. Coordination programming helps to separate concerns, making complex coordination protocols into standalone entities, permitting separate development, verification, maintenance, and reuse. The IWIM coordination model is described, and a formal automata theoretic version of the model is developed, capturing the essentials of the framework in a fibration based approach. Specifically, families of worker automata have their communication governed by a state of a manager automaton, whose transitions correspond to reconfigurations. To capture the generality of processes in IWIM systems, the construction is generalised so that process automata can display both manager and worker traits. The relationship with other formalisations of the IWIM conception of the coordination principle is explored.

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Research Article Tue, 28 Jan 2003 00:00:00 +0200
Membrane Computing: The Power of (Rule) Creation https://lib.jucs.org/article/27867/ JUCS - Journal of Universal Computer Science 8(3): 369-381

DOI: 10.3217/jucs-008-03-0369

Authors: Fernando Arroyo, Angel Baranda, Juan Castellanos, Gheorghe Paun

Abstract: We consider a uniform way of treating objects and rules in P systems: we start with multisets of rules, which are consumed when they are applied, but the application of a rule may also produce rules, to be applied at subsequent steps. We find that this natural and simple feature is surprisingly powerful: systems with only one membrane can characterize the recursively enumerable languages, both in the case of rewriting and of splicing rules, the same result is obtained in the case of symbol-objects, for the recursively enumerable sets of vectors of natural numbers.

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Research Article Thu, 28 Mar 2002 00:00:00 +0200
A Fast and Simple Algorithm for Constructing Minimal Acyclic Deterministic Finite Automata https://lib.jucs.org/article/27865/ JUCS - Journal of Universal Computer Science 8(2): 363-367

DOI: 10.3217/jucs-008-02-0363

Authors: Bruce Watson

Abstract: In this paper, we present a fast and simple algorithm for constructing a minimal acyclic deterministic finite automaton from a denite set of words. Such automata are useful in a wide variety of applications, including computer virus detection, computational linguistics and computational genetics. There are several known algorithms that solve the same problem, though most of the alternative algorithms are considerably more difficult to present, understand and implement than the one given here. Preliminary benchmarking indicates that the algorithm presented here is competitive with the other known algorithms. 1.) C. S. Calude, K. Salomaa, S. Yu (eds.). Advances and Trends in Automata and Formal Languages. A Collection of Papers in Honour of the 60th Birthday of Helmut Jürgensen.

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Research Article Thu, 28 Feb 2002 00:00:00 +0200
How Large is the Set of Disjunctive Sequences? https://lib.jucs.org/article/27864/ JUCS - Journal of Universal Computer Science 8(2): 348-362

DOI: 10.3217/jucs-008-02-0348

Authors: Ludwig Staiger

Abstract: We consider disjunctive sequences, that is, infinite sequences -words) having all finite words as infixes. It is shown that the set of all disjunctive sequences can be described in an easy way using recursive languages and, besides being a set of measure one, is a residual set in Cantor space. Moreover, we consider the subword complexity of sequences: here disjunctive sequences are shown to be sequences of maximal complexity. Along with disjunctive sequences we consider the set of real numbers having disjunctive expansions with respect to some bases and to all bases. The latter are called absolutely disjunctive real numbers. We show that the set of absolutely disjunctive reals is also a residual set and has representations in terms of recursive languages similar to the ones in case of disjunctive sequences. To this end we derive some fundamental properties of the functions translating a base r-expansion of a real [0, 1] into . 1.) C. S. Calude, K. Salomaa, S. Yu (eds.). Advances and Trends in Automata and Formal Languages. A Collection of Papers in Honour of the 60th Birthday of Helmut Jürgensen.

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Research Article Thu, 28 Feb 2002 00:00:00 +0200
Generation of Constants and Synchronization of Finite Automata https://lib.jucs.org/article/27863/ JUCS - Journal of Universal Computer Science 8(2): 332-347

DOI: 10.3217/jucs-008-02-0332

Authors: Arto Salomaa

Abstract: The problem about the synchronization of a finite deterministic automaton is not yet properly understood. The present paper investigates this and related problems within the general framework of a composition theory for functions over a finite domain N with n elements. The notion of depth introduced in this connection is a good indication of the complexity of a given function, namely, the complexity with respect to the length of composition sequences in terms of functions belonging to a basic set. The depth may vary considerably with the target function. Not much is known about the reachability of some target functions, notably constants. Synchronizability of a finite automaton amounts to the representability of some constant as a composition of the functions defined by the input letters. Properties of n such as primality or being a power of 2 turn out to be important, independently of the semantic interpretation. We present some necessary, as well as some sufficient, conditions for synchronizability. We also discuss a famous conjecture about the length of the shortest synchronizing word, and present some results about universal synchronizing words. 1.) C. S. Calude, K. Salomaa, S. Yu (eds.). Advances and Trends in Automata and Formal Languages. A Collection of Papers in Honour of the 60th Birthday of Helmut Jürgensen.

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Research Article Thu, 28 Feb 2002 00:00:00 +0200
On the Power of P Systems with Symport Rules https://lib.jucs.org/article/27862/ JUCS - Journal of Universal Computer Science 8(2): 317-331

DOI: 10.3217/jucs-008-02-0317

Authors: Carlos Martín-Vide, Andrei Paun, Gheorghe Paun

Abstract: A purely communicative variant of P systems was considered recently, based on the trans-membrane transport of couples of chemicals. When using both symport rules (the chemicals pass together in the same direction) and antiport rules (one chemical enters and the other exits a membrane), one obtains the computational completeness, and the question was formulated what happens when only symport rules are considered. We address here this question. First, we surprisingly find that "generalized" symport rules are sufficient: if more than two chemicals pass together through membranes, then we get again the power of Turing machines. Three results of this type are obtained, with a trade-off between the number of chemicals which move together (at least three in the best case) and the number of membranes used. The same result is obtained for standard symport rules (couples of chemicals), if the passing through membranes is conditioned by some permitting contexts (certain chemicals should be present in the membrane). In this case, four membranes suffice. The study of other variants of P systems with symport rules (for instance, with forbidding contexts) is formulated as an open problem. 1.) C. S. Calude, K. Salomaa, S. Yu (eds.). Advances and Trends in Automata and Formal Languages. A Collection of Papers in Honour of the 60th Birthday of Helmut Jürgensen.

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Research Article Thu, 28 Feb 2002 00:00:00 +0200
Tiling the Hyperbolic Plane with a Single Pentagonal Tile https://lib.jucs.org/article/27861/ JUCS - Journal of Universal Computer Science 8(2): 297-316

DOI: 10.3217/jucs-008-02-0297

Authors: Maurice Margenstern

Abstract: In this paper, we study the number of tilings of the hyperbolic plane that can be constructed, starting from a single pentagonal tile, the only permitted transformations on the basic tile being the replication by displacement along the lines of the pentagrid. We obtain that there is no such tiling with five colours, that there are exactly two of them with four colours and a single trivial tiling with one colour. For three colours, the number of solutions depends of the assortment of the colours. For half of them, there is a continuous number of such tilings, for one of them there are four solutions, for the two other ones, there is no such tiling. For two colours, there is always a continuous number of such tilings. By contrast, there is no such analog in the euclidean plane with the similar constraints. 1.) C. S. Calude, K. Salomaa, S. Yu (eds.). Advances and Trends in Automata and Formal Languages. A Collection of Papers in Honour of the 60th Birthday of Helmut Jürgensen.

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Research Article Thu, 28 Feb 2002 00:00:00 +0200
Bridging Two Hierarchies of Infinite Words https://lib.jucs.org/article/27860/ JUCS - Journal of Universal Computer Science 8(2): 292-296

DOI: 10.3217/jucs-008-02-0292

Authors: Solomon Marcus

Abstract: Infinite words on a finite non-empty alphabet have been investigated in various respects. We will consider here two important strategies in approaching such words; one of them proceeds from particular to general, while the other proceeds from general to particular. As we shall see, the respective hierarchies don’t interfer. There is between them an empty space waiting for investigation. 1.) C. S. Calude, K. Salomaa, S. Yu (eds.). Advances and Trends in Automata and Formal Languages. A Collection of Papers in Honour of the 60th Birthday of Helmut Jürgensen.

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Research Article Thu, 28 Feb 2002 00:00:00 +0200
Synchronization and Stability of Finite Automata https://lib.jucs.org/article/27858/ JUCS - Journal of Universal Computer Science 8(2): 270-277

DOI: 10.3217/jucs-008-02-0270

Authors: Jarkko Kari

Abstract: Let G = (V, E) be a strongly connected and aperiodic directed graph of uniform out-degree k. A deterministic finite automaton is obtained if the edges are colored with k colors in such a way that each vertex has one edge of each color leaving it. The automaton is called synchronized if there exists an input word that maps all vertices into the same fixed vertex. The road coloring conjecture asks whether there always exists a coloring such that the resulting automaton is synchronized. The conjecture has been proved for various types of graphs but the general problem remains open. In this work we investigate a related concept of stability, using techniques of linear algebra. We have proved in our earlier papers that the road coloring conjecture is equivalent to the conjecture that each strongly connected and aperiodic graph has a coloring where at least one pair of states is stable. In the present work we prove that stable pairs of states exist in all automata that are almost balanced in the sense that there is at most one state for each color where synchronization can take place. 1.) C. S. Calude, K. Salomaa, S. Yu (eds.). Advances and Trends in Automata and Formal Languages. A Collection of Papers in Honour of the 60th Birthday of Helmut Jürgensen.

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Research Article Thu, 28 Feb 2002 00:00:00 +0200
On Quasi-Products of Tree Automata https://lib.jucs.org/article/27852/ JUCS - Journal of Universal Computer Science 8(2): 184-192

DOI: 10.3217/jucs-008-02-0184

Authors: Ferenc Gécseg

Abstract: In this paper we introduce the concept of the quasi-product of tree automata. In a quasi-product the inputs of the component tree automata are operational symbols in which permutation and unification of variables are allowed. It is shown that in sets of tree automata which are homomorphically complete with respect to the quasi-product the essentially unary operations play the basic role among all operations with nonzero ranks. Furthermore, we give a characterization of homomorphically complete sets which is similar to the classical one. 1.) C. S. Calude, K. Salomaa, S. Yu (eds.). Advances and Trends in Automata and Formal Languages. A Collection of Papers in Honour of the 60th Birthday of Helmut Jürgensen.

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Research Article Thu, 28 Feb 2002 00:00:00 +0200
Additive Distances and Quasi_Distances Between Words https://lib.jucs.org/article/27849/ JUCS - Journal of Universal Computer Science 8(2): 141-152

DOI: 10.3217/jucs-008-02-0141

Authors: Cristian S. Calude, Kai Salomaa, Sheng Yu

Abstract: We study additive distances and quasi-distances between words. We show that every additive distance is finite. We then prove that every additive quasi-distance is regularity-preserving, that is, the neighborhood of any radius of a regular language with respect to an additive quasi-distance is regular. Finally, similar results will be proven for context-free, computable and computably enumerable languages. 1.) C. S. Calude, K. Salomaa, S. Yu (eds.). Advances and Trends in Automata and Formal Languages. A Collection of Papers in Honour of the 60th Birthday of Helmut Jürgensen.

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Research Article Thu, 28 Feb 2002 00:00:00 +0200
The Origins and the Development of the ASM Method for High Level System Design and Analysis https://lib.jucs.org/article/27843/ JUCS - Journal of Universal Computer Science 8(1): 2-74

DOI: 10.3217/jucs-008-01-0002

Authors: Egon Börger

Abstract: The research belonging to the Abstract State Machines approach to system design and analysis is surveyed and documented in an annotated ASM bibliography. The survey covers the period from 1984, when the idea for the concept of ASMs (under the name dynamic or evolving algebras or structures) appears for the first time in a foundational context, to the year 2001 where a mathematically well-founded, practical system development method based upon the notion of ASMs is in place and ready to be industrially deployed. Some lessons for the future of ASMs are drawn.

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Research Article Mon, 28 Jan 2002 00:00:00 +0200
A Neural Abstract Machine https://lib.jucs.org/article/27834/ JUCS - Journal of Universal Computer Science 7(11): 1006-1023

DOI: 10.3217/jucs-007-11-1006

Authors: Egon Börger, Diego Sona

Abstract: In an attempt to capture the fundamental features that are common to neural networks, we define a parameterized Neural Abstract Machine (NAM) in such a way that the major neural networks in the literature can be described as natural extensions or refinements of the NAM. We illustrate the refinement for feedforward networks with back-propagation training. The NAM provides a platform and programming language independent basis for a comparative mathematical and experimental analysis and evaluation of different implementations of neural networks. We concentrate our attention here on the computational core (Neural Kernel NK) and provide abstract interfaces for the other NAM components.

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Research Article Wed, 28 Nov 2001 00:00:00 +0200
Partial Updates: Exploration https://lib.jucs.org/article/27830/ JUCS - Journal of Universal Computer Science 7(11): 917-951

DOI: 10.3217/jucs-007-11-0917

Authors: Yuri Gurevich, Nikolai Tillmann

Abstract: The partial update problem for parallel abstract state machines has manifested itself in the cases of counters, sets and maps. We propose a solution of the problem that lends itself to an efficient implementation and covers the three cases mentioned above. There are other cases of the problem that require a more general framework.

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Research Article Wed, 28 Nov 2001 00:00:00 +0200
New Tools for Cellular Automata in the Hyperbolic Plane https://lib.jucs.org/article/27752/ JUCS - Journal of Universal Computer Science 6(12): 1226-1252

DOI: 10.3217/jucs-006-12-1226

Authors: Maurice Margenstern

Abstract: In this paper, we introduce a new technique in order to deal with cellular automata in the hyperbolic plane. The subject was introduced in [7] which gave an important application of the new possibility opened by the first part of that paper. At the same time, we recall the results that were already obtained in previous papers. Here we go further in these techniques that we opened, and we give new ones that should give better tools to develop the matter.

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Research Article Thu, 28 Dec 2000 00:00:00 +0200
Simulating H Systems by P Systems https://lib.jucs.org/article/27646/ JUCS - Journal of Universal Computer Science 6(1): 178-193

DOI: 10.3217/jucs-006-01-0178

Authors: Gheorghe Paun, Takashi Yokomori

Abstract: H systems are DNA computing models, based on the operation of splicing. P systems are membrane computing models, where objects can evolve in parallel in a hierarchical membrane structure. In particular, the objects can be strings and the evolution rules can be based on splicing. Both H systems with certain controls on the use of splicing rules and P systems of various types are known to be computationally universal, that is, they characterize the recursively ennumerable languages. So, they are equivalent as the generative power. The present paper presents a direct simulation of some controlled H systems by splicing P systems. We achieve this goal for three basic regulation mechanisms: H systems with permitting contexts, H systems with forbidding contexts, and communicating distributed H systems. We can say that in this way we get a uniform implementation of the three types of H systems in the form of a computing cell. 1 C.S.Calude and G.Stefanescu (eds.). Automata, Logic, and Computability. Special issue dedicated to Professor Sergiu Rudeanu Festschrift.

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Research Article Fri, 28 Jan 2000 00:00:00 +0200
Computational Complementarity and Shift Spaces https://lib.jucs.org/article/27644/ JUCS - Journal of Universal Computer Science 6(1): 169-177

DOI: 10.3217/jucs-006-01-0169

Authors: Marjo Lipponen

Abstract: Computational complementarity was introduced to mimic the physical complementarity in terms of finite automata (with outputs but no initial state). Most of the work has been focussed on "frames", i.e., on fixed, static, local descriptions of the system behaviour. The first paper aiming to study the asymptotical description of complementarity was restricted to certain types of sofic shifts. In this paper we continue this work and extend the results to all irreducible sofic shifts. We also study computational complementarity in terms of labelled graphs rather than automata. 1 C.S.Calude and G.Stefanescu (eds.). Automata, Logic, and Computability. Special issue dedicated to Professor Sergiu Rudeanu Festschrift.

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Research Article Fri, 28 Jan 2000 00:00:00 +0200
Splicing on Trees: the Iterated Case https://lib.jucs.org/article/27596/ JUCS - Journal of Universal Computer Science 5(9): 599-609

DOI: 10.3217/jucs-005-09-0599

Authors: George Rahonis

Abstract: The closure under the splicing operation with finite and recognizable sets of rules, is extended to the family of generalized synchronized forests. Moreover, we investigate the application of the iterated splicing on known families of forests. Interesting properties of this operation are established.

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Research Article Tue, 28 Sep 1999 00:00:00 +0300
Decomposition of Timed Automata https://lib.jucs.org/article/27590/ JUCS - Journal of Universal Computer Science 5(9): 574-587

DOI: 10.3217/jucs-005-09-0574

Authors: Kahn Mason, Padmanabhan Krishnan

Abstract: In this paper we extend the notion of homomorphisms and decomposition to timed automata. This is based on the classical Hartmanis-Stearns decomposition results for finite state automata. As in the classical theory, the existence of non-trivial orthogonal partitions is both necessary and sufficient for non-trivial decompositions. Of course, now these partitions have to include both the set of states and the set of timers (or clocks) in the system. We present an example which illustrate the various issues.

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Research Article Tue, 28 Sep 1999 00:00:00 +0300
A Polynomial Solution for 3-SAT in the Space of Cellular Automata in the Hyperbolic Plane https://lib.jucs.org/article/27589/ JUCS - Journal of Universal Computer Science 5(9): 563-573

DOI: 10.3217/jucs-005-09-0563

Authors: Maurice Margenstern, Kenichi Morita

Abstract: In this paper, we define cellular automata on a grid of the hyperbolic plane, based on the tessellation obtained from the regular pentagon with right angles. Taking advantage of the properties of that grid, we show that 3-SAT can be solved in polynomial time in that setting, and then we extend that result for any NP problem. Several directions starting from that result are indicated.

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Research Article Tue, 28 Sep 1999 00:00:00 +0300
Issues Related to Distributed Processing of Picture Languages https://lib.jucs.org/article/27587/ JUCS - Journal of Universal Computer Science 5(9): 542-551

DOI: 10.3217/jucs-005-09-0542

Authors: Padmanabhan Krishnan

Abstract: In this article we show that the parallel processing of pictures requires extending the notion of pictures with blank spaces. For the purposes of this article, parallel processing is defined in terms of a product construction.

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Research Article Tue, 28 Sep 1999 00:00:00 +0300
Minimal Deterministic Incomplete Automata https://lib.jucs.org/article/27429/ JUCS - Journal of Universal Computer Science 3(11): 1180-1193

DOI: 10.3217/jucs-003-11-1180

Authors: Elena Calude, Mario Lipponen

Abstract: We construct a minimal automaton for an output-incomplete Moore automaton. The approach is motivated by physical interpretation of seeing deterministic finite automata as models for elementary particles. When compared to some classical methods our minimal automaton is unique up to an isomorphism and preserves also the undefined or unspecified behaviour of the original automaton. 1.) Proceedings of the First Japan--New Zealand Workshop on Logic in Computer Science, special issue editors D.S. Bridges, C.S. Calude, M.J. Dinneen and B. Khoussainov. 2.)On leave from the Department of Mathematics, University of Turku, Finland.

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Research Article Fri, 28 Nov 1997 00:00:00 +0200
Recursive Abstract State Machines https://lib.jucs.org/article/27347/ JUCS - Journal of Universal Computer Science 3(4): 233-246

DOI: 10.3217/jucs-003-04-0233

Authors: Yuri Gurevich, Marc Spielmann

Abstract: According to the ASM thesis, any algorithm is essentially a Gurevich abstract state machine. The only objection to this thesis, at least in its sequential version, has been that ASMs do not capture recursion properly. To this end, we suggest recursive ASMs. 1.) Partially supported by NSF grant CCR 95-04375 and ONR grant N00014-94-1-1182. 2.) Visiting scholar at the University of Michigan, partially supported by DAAD and The University of Michigan.

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Research Article Mon, 28 Apr 1997 00:00:00 +0300
Conditional Branching is not Necessary for Universal Computation in von Neumann Computers https://lib.jucs.org/article/27304/ JUCS - Journal of Universal Computer Science 2(11): 756-768

DOI: 10.3217/jucs-002-11-0756

Authors: Raul Rojas

Abstract: In this paper we discuss the issue of the minimal instruction set necessary for universal computation. Our computing model is a machine consisting of a processor with a single n-bit register and a separate memory of n-bit words. We show that four simple instructions are sufficient in order to evaluate any computable function. Such reduction of the instruction set can only be achieved by exploiting the properties of self-modifying programs. Then we prove that, surprisingly, conditional branching can be substituted by unconditional branching. This is the main result of this paper. Therefore any computable function can be computed using only the instructions LOAD, STORE, INC and GOTO (unconditional branching). We also show that externally stored looping programs using indirect addressing and no branches are as powerful as conventional computer programs.

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Research Article Thu, 28 Nov 1996 00:00:00 +0200
Ceilings of Monotone Boolean Functions https://lib.jucs.org/article/27271/ JUCS - Journal of Universal Computer Science 2(7): 533-548

DOI: 10.3217/jucs-002-07-0533

Authors: Paul Dunne

Abstract: This paper considers a particular relationship defined overpairs of n-argument monotone Boolean functions. The relationship is of interest since we can show that if ( g, h ) satisfy it then for any n-argument monotone Boolean function f there is a close relationship between the combinational and monotone network complexities of the function (f/\g) \/ h. We characterise the class of pairs of functions satisfying the relationship and show that it extends and encapsulates previous results concerning translations from combinational to monotone networks.

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Research Article Sun, 28 Jul 1996 00:00:00 +0300
The Power of Restricted Splicing with Rules from a Regular Language https://lib.jucs.org/article/27235/ JUCS - Journal of Universal Computer Science 2(4): 224-240

DOI: 10.3217/jucs-002-04-0224

Authors: Lila Kari, Gheorghe Paun, Arto Salomaa

Abstract: We continue the investigations begun in [11] on the relationships between several variants of the splicing operation and usual operations with formal languages. The splicing operations are defined with respect to arbitrarily large sets of splicing rules, codified as simple languages. The closure properties of families in Chomsky hierarchy are examined in this context. Several surprising results are obtained about the generative or computing power of the splicing operation. Many important open problems are mentioned.

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Research Article Sun, 28 Apr 1996 00:00:00 +0300
An Aperiodic Set of Wang Cubes https://lib.jucs.org/article/27167/ JUCS - Journal of Universal Computer Science 1(10): 675-686

DOI: 10.3217/jucs-001-10-0675

Authors: Karel Ii., Jarkko Kari

Abstract: We introduce Wang cubes with colored faces that are a generalization of Wang tiles with colored edges. We show that there exists an aperiodic set of 21 Wang cubes, that is, a set for which there exists a tiling of the whole space with matching unit cubes but there exists no periodic tiling. We use the aperiodic set of 13 Wang tiles recently obtained by the first author using the new method developed by the second. Our method can be used to construct an aperiodic set of n-dimensional cubes for any n 3.

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Research Article Sat, 28 Oct 1995 00:00:00 +0200