Latest Articles from JUCS - Journal of Universal Computer Science Latest 61 Articles from JUCS - Journal of Universal Computer Science https://lib.jucs.org/ Thu, 28 Mar 2024 11:46:38 +0200 Pensoft FeedCreator https://lib.jucs.org/i/logo.jpg Latest Articles from JUCS - Journal of Universal Computer Science https://lib.jucs.org/ MODELFY: A Model-driven Solution for Decision Making based on Fuzzy Information https://lib.jucs.org/article/76030/ JUCS - Journal of Universal Computer Science 28(5): 445-474

DOI: 10.3897/jucs.76030

Authors: María Castañeda, Mercedes G. Merayo, Juan Boubeta-Puig, Iván Calvo

Abstract: There exist areas, such as the disease prevention or inclement weather protocols, in which the analysis of the information based on strict protocols require a high level of rigor and security. In this situation, it would be desirable to apply formal methodologies that provide these features. In this scope, recently, it has been proposed a formalism, fuzzy automaton, that captures two relevant aspects for fuzzy information analysis: imprecision and uncertainty. However, the models should be designed by domain experts, who have the required knowledge for the design of the processes, but do not have the necessary technical knowledge. To address this limitation, this paper proposes MODELFY, a novel model-driven solution for designing a decision-making process based on fuzzy automata that allows users to abstract from technical complexities. With this goal in mind, we have developed a framework for fuzzy automaton model design based on a Domain- Specific Modeling Language (DSML) and a graphical editor. To improve the interoperability and functionality of this framework, it also includes a model-to-text transformation that translates the models designed by using the graphical editor into a format that can be used by a tool for data anal- ysis. The practical value of this proposal is also evaluated through a non-trivial medical protocol for detecting potential heart problems. The results confirm that MODELFY is useful for defining such a protocol in a user-friendly and rigorous manner, bringing fuzzy automata closer to domain experts.

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Research Article Sat, 28 May 2022 10:00:00 +0300
On Recurrent Neural Network Based Theorem Prover For First Order Minimal Logic https://lib.jucs.org/article/76563/ JUCS - Journal of Universal Computer Science 27(11): 1193-1202

DOI: 10.3897/jucs.76563

Authors: Ashot Baghdasaryan, Hovhannes Bolibekyan

Abstract: There are three main problems for theorem proving with a standard cut-free system for the first order minimal logic. The first problem is the possibility of looping. Secondly, it might generate proofs which are permutations of each other. Finally, during the proof some choice should be made to decide which rules to apply and where to use them. New systems with history mechanisms were introduced for solving the looping problems of automated theorem provers in the first order minimal logic. In order to solve the rule selection problem, recurrent neural networks are deployed and they are used to determine which formula from the context should be used on further steps. As a result, it yields to the reduction of time during theorem proving.

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Research Article Sun, 28 Nov 2021 10:00:00 +0200
Regular Expressions with Lookahead https://lib.jucs.org/article/66330/ JUCS - Journal of Universal Computer Science 27(4): 324-340

DOI: 10.3897/jucs.66330

Authors: Martin Berglund, Brink van der Merwe, Steyn van Litsenborgh

Abstract: This paper investigates regular expressions which in addition to the standard operators of union, concatenation, and Kleene star, have lookaheads. We show how to translate regular expressions with lookaheads (REwLA) to equivalent Boolean automata having at most 3 states more than the length of the REwLA. We also investigate the state complexity when translating REwLA to equivalent deterministic finite automata (DFA).

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Research Article Wed, 28 Apr 2021 19:30:00 +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
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
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
An Algebraic Theory of Epistemic Processes https://lib.jucs.org/article/23554/ JUCS - Journal of Universal Computer Science 19(10): 1396-1432

DOI: 10.3217/jucs-019-10-1396

Authors: Hamid Mahrooghi, Rasool Jalili

Abstract: In the past few years, several process-algebraic frameworks have been proposed that incorporate the notion of epistemic knowledge. These frameworks allow for reasoning about knowledge-related properties, such as anonymity, secrecy and authentication, in the operational specifications given in process-algebraic languages. Hitherto, no sound and (ground-)complete axiomatization has been given for the abovementioned process-algebraic frameworks. In this paper, we define notions of bisimulation that are suitable for such process algebras with histories and give a sound and ground-complete axiomatization for the theory of CryptoPAi, which is a process algebra based on Milner's Calculus of Communicating Systems (CCS) extended with cryptographic terms and identities. Moreover, we show that one of our defined notions of bisimulation is precisely characterized by the extension of the Hennessy-Milner logic with epistemic constructs.

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Research Article Tue, 28 May 2013 00:00:00 +0300
Crossing the Undecidability Border with Extensions of Propositional Neighborhood Logic over Natural Numbers https://lib.jucs.org/article/23980/ JUCS - Journal of Universal Computer Science 18(20): 2798-2831

DOI: 10.3217/jucs-018-20-2798

Authors: Dario Monica, Valentin Goranko, Angelo Montanari, Guido Sciavicco

Abstract: Propositional Neighborhood Logic (PNL) is an interval temporal logic featuring two modalities corresponding to the relations of right and left neighborhood between two intervals on a linear order (in terms of Allen's relations, meets/ and met by). Recently, it has been shown that PNL interpreted over several classes of linear orders, including natural numbers, is decidable (NEXPTIME-complete) and that some of its natural extensions preserve decidability. Most notably, this is the case with PNL over natural numbers extended with a limited form of metric constraints and with the future fragment of PNL extended with modal operators corresponding to Allen's relations begins, begun by, and before/. This paper aims at demonstrating that PNL and its metric version MPNL, interpreted over natural numbers, are indeed very close to the border with undecidability, and even relatively weak extensions of them become undecidable. In particular, we show that (i) the addition of binders on integer variables ranging over interval lengths makes the resulting hybrid extension of MPNL undecidable, and (ii) a very weak first-order extension of the future fragment of PNL, obtained by replacing proposition letters by a restricted subclass of first-order formulae where only one variable is allowed, is undecidable (in contrast with the decidability of similar first-order extensions of point-based temporal logics).

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Research Article Sat, 1 Dec 2012 00:00:00 +0200
Towards Model-Driven Engineering Support for Service Evolution https://lib.jucs.org/article/23935/ JUCS - Journal of Universal Computer Science 18(17): 2364-2382

DOI: 10.3217/jucs-018-17-2364

Authors: Juan Vara, Vasilios Andrikopoulos, Michael Papazoglou, Esperanza Marcos

Abstract: In the field of Service-Oriented Architecture (SOA) evolution is a key issue given the non-trivial nature of updating widely distributed and heterogeneous systems. With this in mind, in this work we used some of the technologies developed in the context of the Eclipse Modeling Framework (EMF) to provide a proof of concept of the possible synergy between Model-Driven Engineering (MDE) and Service Orientation. In particular, we present a DSL toolkit for modeling the structural part of Abstract Service Descriptions (ASDs) and the reasoning mechanism that assesses whether two versions of a service are compatible with respect to its consumers.

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Research Article Sat, 1 Sep 2012 00:00:00 +0300
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
Array P System with Shuffle on Trajectories https://lib.jucs.org/article/23795/ JUCS - Journal of Universal Computer Science 18(13): 1802-1820

DOI: 10.3217/jucs-018-13-1802

Authors: A. S. Venkatesan, D. G. Thomas, T. Robinson, Atulya Nagar

Abstract: In this paper, we introduce a new concept of trajectory array P system which consists of a membrane structure in which the objects are arrays and the evolutionary rules are given in terms of trajectories. We present some properties of trajectory array P system and compare with certain families of picture languages. We consider a variant of trajectory array P system and show that the languages generated by the trajectory P system and its variant have common intersection.

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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
Modeling and Performance Evaluation of a Contract-based Electronic Signature Process https://lib.jucs.org/article/23168/ JUCS - Journal of Universal Computer Science 18(5): 676-703

DOI: 10.3217/jucs-018-05-0676

Authors: Ahmed Nait-Sidi-Moh, Mohamed Bakhouya, Wafaa Ait-Cheik-Bihi, Jaafar Gaber

Abstract: Distributed systems become ubiquitous by allowing users access to a wide range of services at any time, anywhere, and from a variety of devices. In these open environments where there are many opportunities for both fraudulent services and misbehaving clients, service discovery systems are subject to security challenges. Controlling services' access is one of the fundamental issues that must be faced in the context of service discovery in distributed and open environments. Therefore, secure accesses and utilization of available services must be ensured for users. In our previous work, a contract-based approach for controlling the service access in a distributed computing context was presented. In this paper, we address the purpose and the usage of digital signature on negotiated electronic queries between a server and clients in service discovery systems and web service composition. The paper discusses the combined use of Timed Event Graphs and (max, +)- algebra to model, evaluate and optimize the performance of the signature process and client requests validation by a service provider (server). Based on an optimization resource allocation algorithm, an improvement study of the quality of service offered to the clients, in terms of waiting times and validation of their requests, is proposed. The results are reported and show the efficiency of the use of the proposed formal tools for performance analysis, evaluation and tuning of the considered process.

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Research Article Thu, 1 Mar 2012 00:00:00 +0200
Hierarchical Graph-Grammar Model for Secure and Efficient Handwritten Signatures Classification https://lib.jucs.org/article/29945/ JUCS - Journal of Universal Computer Science 17(6): 926-943

DOI: 10.3217/jucs-017-06-0926

Authors: Marcin Piekarczyk, Marek Ogiela

Abstract: One important subject associated with personal authentication capabilities is the analysis of handwritten signatures. Among the many known techniques, algorithms based on linguistic formalisms are also possible. However, such techniques require a number of algorithms for intelligent image analysis to be applied, allowing the development of new solutions in the field of personal authentication and building modern security systems based on the advanced recognition of such patterns. The article presents the approach based on the usage of syntactic methods for the static analysis of handwritten signatures. The graph linguistic formalisms applied, such as the IE graph and ETPL(k) grammar, are characterised by considerable descriptive strength and a polynomial membership problem of the syntactic analysis. For the purposes of representing the analysed handwritten signatures, new hierarchical (two-layer) HIE graph structures based on IE graphs have been defined. The two-layer graph description makes it possible to take into consideration both local and global features of the signature. The usage of attributed graphs enables the storage of additional semantic information describing the properties of individual signature strokes. The verification and recognition of a signature consists in analysing the affiliation of its graph description to the language describing the specimen database. Initial assessments display a precision of the method at a average level of under 75%.

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Research Article Mon, 28 Mar 2011 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
A Note on the P-completeness of Deterministic One-way Stack Language https://lib.jucs.org/article/29639/ JUCS - Journal of Universal Computer Science 16(5): 795-799

DOI: 10.3217/jucs-016-05-0795

Authors: Klaus-Jörn Lange

Abstract: The membership problems of both stack automata and nonerasing stack automata are shown to be complete for polynomial time.

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Research Article Mon, 1 Mar 2010 00:00:00 +0200
On the Linear Number of Matching Substrings https://lib.jucs.org/article/29628/ JUCS - Journal of Universal Computer Science 16(5): 715-728

DOI: 10.3217/jucs-016-05-0715

Authors: Yo-Sub Han

Abstract: We study the number of matching substrings in the pattern matching problem. In general, there can be a quadratic number of matching substrings in the size of a given text. The linearizing restriction enables to find at most a linear number of matching substrings. We first explore two well-known linearizing restriction rules, the longest-match rule and the shortest-match substring search rule, and show that both rules give the same result when a pattern is an infix-free set even though they have different semantics. Then, we introduce a new linearizing restriction, the leftmost nonoverlapping match rule that is suitable for find-and-replace operations in text searching, and propose an efficient algorithm for the new rule when a pattern is described by a regular expression. We also examine the problem of obtaining the maximal number of non-overlapping matching substrings.

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Research Article Mon, 1 Mar 2010 00:00:00 +0200
Orthogonal Concatenation: Language Equations and State Complexity https://lib.jucs.org/article/29624/ JUCS - Journal of Universal Computer Science 16(5): 653-675

DOI: 10.3217/jucs-016-05-0653

Authors: Mark Daley, Michael Domaratzki, Kai Salomaa

Abstract: A language L is the orthogonal concatenation of languages L1 and L2 if every word of L can be written in a unique way as a concatenation of a word in L1 and a word in L2. The notion can be generalized for arbitrary language operations. We consider decidability properties of language orthogonality and the solvability of language equations involving the orthogonal concatenation operation. We establish a tight bound for the state complexity of orthogonal concatenation of regular languages.

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Research Article Mon, 1 Mar 2010 00:00:00 +0200
Multi-criteria Group Decision Support with Linguistic Variables in Long-term Scenarios for Belgian Energy Policy https://lib.jucs.org/article/29577/ JUCS - Journal of Universal Computer Science 16(1): 103-120

DOI: 10.3217/jucs-016-01-0103

Authors: Da Ruan, Jie Lu, Erik Laes, Guangquan Zhang, Jun Ma, Gaston Meskens

Abstract: Real world decisions often made in the presence of multiple, conflicting, and incommensurate criteria. Decision making requires multiple perspectives of different individuals as more decisions are made now in groups than ever before. This is particularly true when the decision environment becomes more complex such as sustainability policies study in environmental and energy sectors. Group decision making processes judgments or solutions for decision problems based on the input and feedback of multiple individuals. Multi-criteria decision and evaluation problems at tactical and strategic levels in practice involve fuzziness in terms of linguistic variables vis-à-vis criteria, weights, and decision maker judgments. Relevant alternatives or scenarios are evaluated according to a number of desired criteria. A fuzzy multi-criteria group decision software tool is developed to analyze long-term scenarios for Belgian energy policy in this paper.

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Research Article Fri, 1 Jan 2010 00:00:00 +0200
Petri Net Controlled Grammars: the Case of Special Petri Nets https://lib.jucs.org/article/29521/ JUCS - Journal of Universal Computer Science 15(14): 2808-2835

DOI: 10.3217/jucs-015-14-2808

Authors: Jürgen Dassow, Sherzod Turaev

Abstract: A Petri net controlled grammar is a context-free grammar equipped with a Petri net, whose transitions are labeled with rules of the grammar or the empty string, and the associated language consists of all terminal strings which can be derived in the grammar and the the sequence of rules in every terminal derivation corresponds to some occurrence sequence of transitions of the Petri net which is enabled at the initial marking and finished at a final marking of the net. We present some results on the generative capacity of such grammars so that the associated Petri nets are restricted to some known special classes of Petri nets.

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Research Article Sat, 1 Aug 2009 00:00:00 +0300
On Finite-time Computability Preserving Conversions https://lib.jucs.org/article/29392/ JUCS - Journal of Universal Computer Science 15(6): 1365-1380

DOI: 10.3217/jucs-015-06-1365

Authors: Hideki Tsuiki, Shuji Yamada

Abstract: A finite-time computable function is a partial function from ∑ω to ∑ ω whose value is constructed by concatenating a finite list with a suffix of the argument. A finite-time computability preserving conversion α : X → Y for X, Y ⊂ ∑ω is a bijection which preserves finite-time computability. We show that all the finite-time computability preserving conversions with the domain ∑ω are extended sliding block functions.

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Research Article Sat, 28 Mar 2009 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
Visualization and Manipulation of Incomplete and Uncertain Dependencies by Decision Diagrams https://lib.jucs.org/article/28509/ JUCS - Journal of Universal Computer Science 11(11): 1849-1862

DOI: 10.3217/jucs-011-11-1849

Authors: Denis Popel

Abstract: The data mining community is focused on a variety of methods and algorithms to manipulate incompletely specified or uncertain data and their dependencies. The major obstacle in the representation and visualization of incompletely specified data is the size explosion problem through defining undefined or uncertain values, which commonly raises questions about suggested heuristics and their practical applicability. Recently, there is a renewed interest in resolving the size explosion problem for incompletely specified and uncertain data based on symbolic techniques. One of such techniques, decision diagram, has been successfully applied to many knowledge visualization and data manipulation problems.

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Research Article Mon, 28 Nov 2005 00:00:00 +0200
Tools for Parametric Verification. A Comparison on a Case Study https://lib.jucs.org/article/28314/ JUCS - Journal of Universal Computer Science 10(10): 1469-1494

DOI: 10.3217/jucs-010-10-1469

Authors: Petr Matoušek

Abstract: Protocol analysis involves several parameters in model specification, for instance, transmission delay or the length of the transmitting window. Verification of the model with parameters is a semi-decision process that depends on the number of clocks, parameters and counters in the model. Using combination of different verification tools for timed models as HyTech, TReX and UPPaal we are able to find relation between parameters satisfying desired property. The paper gives a report on the synthesis of parameters of PGM protocol. We built a formal model based on extended time automata with parameters and verified the reliability property. Our results automatically obtained from the model are consistent with previous results derived manually. The paper describes our experience with parametric verification of multicast protocol PGM. Results mentioned in the work were made with collaboration with Mihaela Sighireanu (Mihaela.Sighireanu@liafa.jussieu.fr) from LIAFA, Paris.

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Research Article Thu, 28 Oct 2004 00:00:00 +0300
Rewriting Tissue P Systems https://lib.jucs.org/article/28296/ JUCS - Journal of Universal Computer Science 10(9): 1250-1271

DOI: 10.3217/jucs-010-09-1250

Authors: Madhu Mutyam, Vaka Prakash, Kamala Krithivasan

Abstract: By considering string-objects and rewriting rules, we propose a variant of tissue P systems, namely, rewriting tissue P systems. We show the computational efficiency of rewriting tissue P systems by solving the Satisfiability and the Hamiltonian path problems in linear time. We study the computational capacity of rewriting tissue P systems and show that rewriting tissue P systems with at most two cells and four states are computationally universal. We also show the universality result of rewriting tissue P systems with at most one cell and five states. Finally we propose some new directions for future work.

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Research Article Tue, 28 Sep 2004 00:00:00 +0300
On P Systems with Promoters/Inhibitors https://lib.jucs.org/article/28234/ JUCS - Journal of Universal Computer Science 10(5): 581-599

DOI: 10.3217/jucs-010-05-0581

Authors: Mihai Ionescu, Dragos Sburlan

Abstract: This article shows how the computational universality can be reached using P systems with object rewriting non-cooperative rules, promoters/inhibitors at the level of rules, and only one catalyst. Both generative and accepting cases are studied. The theoretical issues presented are illustrated by several examples.

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Research Article Fri, 28 May 2004 00:00:00 +0300
P Systems with Symport/Antiport of Rules https://lib.jucs.org/article/28227/ JUCS - Journal of Universal Computer Science 10(5): 540-558

DOI: 10.3217/jucs-010-05-0540

Authors: Matteo Cavaliere, Daniela Genova

Abstract: Moving "instructions" instead of "data" using transport mechanisms inspired by biology is the basic idea of the computing device presented in this paper. Specifically, we propose a new class of P systems that use both evolution rules and symport/antiport rules. The idea of this kind of systems is the following: during a computation, symbol-objects (the "data") evolve using evolution rules, but they cannot be moved, on the other hand, the evolution rules (the "instructions") can be moved across the membranes using classical symport/antiport rules. We present a number of results using different combinations of evolution rules (catalytic, non-cooperative) and the weight of the symport/antiport rules. In particular, we show that using non-cooperative rules and antiports of unbounded weight makes it possible to obtain at least the Parikh set of ET0L languages. On the other hand, using catalytic rules (one catalyst) and antiports of weight 2, these system become universal. Several open problems are also presented.

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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
On Determinism of Evolution-Communication P Systems https://lib.jucs.org/article/28223/ JUCS - Journal of Universal Computer Science 10(5): 502-508

DOI: 10.3217/jucs-010-05-0502

Authors: Artiom Alhazov

Abstract: It is commonly believed that a significant part of the computational power of membrane systems comes from their inherent non-determinism. Recently, R. Freund and Gh. Paun have considered deterministic P systems, and formulated the general question whether the computing (generative) capacity of non-deterministic P systems is strictly larger than the (accepting) capacity of their deterministic counterpart. In this paper, we study the computational power of deterministic P systems in the evolution{communication framework. It is known that, in the generative case, two membranes are enough for universality. For the deterministic systems, we obtain the universality with three membranes, leaving the original problem open.

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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
Reasoning about Propagation of Properties over Regions https://lib.jucs.org/article/28110/ JUCS - Journal of Universal Computer Science 9(9): 1030-1045

DOI: 10.3217/jucs-009-09-1030

Authors: Kazuko Takahashi

Abstract: We discuss how a property of some region is propagated to other regions. We propose a system called SRCC that enables the integration of spatial and semantic data. SRCC can represent the relative positions of regions, properties that hold in some regions, semantic relation between regions, and so on. We define the model and describe an algorithm that checks for the existence of a model for a given set of formulas based on this model. We prove the soundness and completeness of the algorithm and apply it to an example that inspects the causality of contamination in 2D space.

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Research Article Sun, 28 Sep 2003 00:00:00 +0300
On the Simplification of HD0L Power Series https://lib.jucs.org/article/27922/ JUCS - Journal of Universal Computer Science 8(12): 1040-1046

DOI: 10.3217/jucs-008-12-1040

Authors: Juha Honkala

Abstract: Nielsen, Rozenberg, Salomaa and Skyum have shown that HD0L languages are CPDF0L languages. We will generalize this result for formal power series. We will also give a new proof of the result of Nielsen, Rozenberg, Salomaa and Skyum.

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Research Article Sat, 28 Dec 2002 00:00:00 +0200
Heyting Algebras and Formal Languages https://lib.jucs.org/article/27898/ JUCS - Journal of Universal Computer Science 8(7): 722-736

DOI: 10.3217/jucs-008-07-0722

Authors: Werner Kuich, Norbert Sauer, Friedrich Urbanek

Abstract: By introducing a new operation, the exponentiation of formal languages, we can define Heyting algebras of formal languages. It turns out that some well known families of languages are closed under this exponentiation, e. g., the families of regular and of context-sensitive languages.

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Research Article Sun, 28 Jul 2002 00:00:00 +0300
Modelling Agents as Observable Sources https://lib.jucs.org/article/27872/ JUCS - Journal of Universal Computer Science 8(4): 423-452

DOI: 10.3217/jucs-008-04-0423

Authors: Mirko Viroli, Andrea Omicini

Abstract: Observation is a fundamental interaction pattern in today's computer-based systems. Adopting observation as the main modelling criterion, computer-based systems can be represented as composed by three class of entities: observers, observables (or sources), and coordinators, that is, the entities managing the observer/source interaction. Also, agents and agent societies are fundamental abstractions in modelling today's complex systems. When exploiting observation in the context of agent-based systems, the most natural interpretation for agents is to see them as either observers or coordinators. However, their situatedness and autonomy, their peculiar perception and representation of the environment, and their typical ability to infer new knowledge - in short, their individual viewpoint over the world -, make agents suitable for an interpretation as observable sources. Accordingly, this paper discusses the implications of using observation to model agent systems, and focuses on the interpretation of agents as observables. A formal framework is developed where multiagent systems are modelled as the composition of agents interacting by observing each other and by mutually affecting their observable behaviour.

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Research Article Sun, 28 Apr 2002 00:00:00 +0300
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
Some Remarks on Codes Defined by Petri Nets https://lib.jucs.org/article/27857/ JUCS - Journal of Universal Computer Science 8(2): 260-269

DOI: 10.3217/jucs-008-02-0260

Authors: Masami Ito, Jürgen Dassow, Ralf Stiebe

Abstract: With any Petri net we associated its CPN language which consists of all sequences of transitions which reach a marking with an empty place whereas all proper prefixes of the sequence lead to positive markings. We prove that any CPN language can be accepted by a partially blind multicounter machine, and that any partially blind multicounter language is the morphic image of some CPN language. As a corollary we obtain the decidability of membership, emptiness and finiteness problem for CPN languages. We characterize the very strictly bounded regular languages, which are CPN languages, and give a condition for a Petri net, which ensures that its generated language is regular. We give a dense CPN language and prove that no dense regular language is a CPN language. 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
Word Operation Closure and Primitivity of Languages https://lib.jucs.org/article/27855/ JUCS - Journal of Universal Computer Science 8(2): 243-256

DOI: 10.3217/jucs-008-02-0243

Authors: H. Hsiao, C. Huang, S. Yu

Abstract: Based on the general operation of words, called bw_operation, the notions of primitive words, closed languages, bases of languages and operation_left_quotient_closed languages are defined and investigated. These notions turn out to be generalizations of the classical notions of primitive words, plus_closed (star_closed) languages, minimal generating sets and deletion_closed languages. Properties of the set of all primitive words, the bases of non_empty languages, right residuals and operation_left_quotient closed languages are studied under the general concept of word operation. Properties of bi_catenation and related languages are discussed as examples and also by their own interests. 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
Rationally Additive Semirings https://lib.jucs.org/article/27851/ JUCS - Journal of Universal Computer Science 8(2): 173-183

DOI: 10.3217/jucs-008-02-0173

Authors: Zoltán Ésik, Werner Kuich

Abstract: We define rationally additive semirings that are a generalization of (ω)-complete and (ω)-continuous semirings. We prove that every rationally additive semiring is an iteration semiring. Moreover, we characterize the semirings of rational power series with coefficients in , the semiring of natural numbers equipped with a top element, as the free rationally additive semirings 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
On the Computational Complexity of Synchronized Context-Free Languages https://lib.jucs.org/article/27848/ JUCS - Journal of Universal Computer Science 8(2): 119-140

DOI: 10.3217/jucs-008-02-0119

Authors: Henning Bordihn, Markus Holzer

Abstract: We introduce counter synchronized contextfree grammars and investigate their generative power. It turns out that the family of counter synchronized contextfree languages is a proper superset of the family of contextfree languages and is strictly contained in the family of synchronized contextfree languages. Moreover, we establish the space and time complexity of the fixed membership, the general membership, and the nonemptiness problem for synchronized and counter synchronized contextfree languages and solve the mentioned complexity questions in terms of completeness results for complexity classes. In this way we present new complete problems for LOG(CF), NP, and PSpace. It is worth to mention that the main theorem on the PSpacecompleteness of the general membership problem of synchronized contextfree grammars relies on a remarkable normal form for these grammars, namely for every synchronized contextfree grammar one can effectively construct and equivalent grammar of same type without nonsynchronizing nonterminals, except the axiom. 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
Formal Definition of SDL-2000 - Compiling and Running SDL Specifications as ASM Models https://lib.jucs.org/article/27835/ JUCS - Journal of Universal Computer Science 7(11): 1024-1049

DOI: 10.3217/jucs-007-11-1024

Authors: Robert Eschbach, Uwe Glässer, Reinhard Gotzhein, Martin Löwis, Andreas Prinz

Abstract: In November 1999, the current version of SDL (Specification and Description Language), commonly referred to as SDL-2000, has passed ITU-T, an international standardization body for telecommunication. The importance and acceptance of SDL in the telecommunication industry surpasses that of UML, which can be seen as the major competitor. A crucial difference between SDL and UML is the existence of a formal SDL semantics as part of the international standard, which has a positive impact on the quality of the entire language definition. In this paper, we treat fundamental questions concerning practicability, adequacy and maintainability of the formalization approach, provide insights into the formal semantics definition and point out several effects on the SDL standard.

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Research Article Wed, 28 Nov 2001 00:00:00 +0200
Three Variants of the DT0L Sequence Equivalence Problem https://lib.jucs.org/article/27825/ JUCS - Journal of Universal Computer Science 7(10): 886-892

DOI: 10.3217/jucs-007-10-0886

Authors: Juha Honkala

Abstract: We discuss three variants of the DT0L sequence equivalence problem. One of the variants generalizes the sequence equivalence problem of D0L systems for DT0L systems.

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Research Article Sun, 28 Oct 2001 00:00:00 +0300
On Teaching Software Engineering based on Formal Techniques - Thoughts about and Plans for - A Different Software Engineering Text Book https://lib.jucs.org/article/27811/ JUCS - Journal of Universal Computer Science 7(8): 641-667

DOI: 10.3217/jucs-007-08-0641

Authors: Dines Bjørner

Abstract: We present the didactic bases for a different kind of text book on Software Engineering - one that is based on semiotics, proper description principles, informal narrations and formal specifications, on phase, stage and stepwise development from developing understandings of the domain, via requirements to software design. Each of the concepts: Semiotics, description, documents, abstraction & modelling, domains, requirements and software design, are covered systematically while enunciating a number of method principles for selecting and applying techniques and tools for the effcient construction of efficient software. The proposed textbook presents many, what are believed to be novel development concepts: Domain engineering with its emphasis on domain attributes, stake{holder perspectives and domain facets (intrinsics, support technologies, management & organization, rules & regulation, human behaviour, etc.), requirements engineering with its decomposition into domain requirements (featuring such techniques as projection, instantiation, extension and initialization), interface requirements and machine requirements, etc.

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Research Article Tue, 28 Aug 2001 00:00:00 +0300
Some Elements of Z Specification Style: Structuring Techniques https://lib.jucs.org/article/27747/ JUCS - Journal of Universal Computer Science 6(12): 1203-1225

DOI: 10.3217/jucs-006-12-1203

Authors: Anthony Macdonald, David Carrington

Abstract: This article investigates the issue of structuring Z specifications. It uses examples from a large specification (the production cell) to examine both conventions for using Z and notational extensions, including Object-Z. Because of the importance of good structure within a specification, specifiers need to be aware of a range of structuring techniques and understand where each is applicable.

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Research Article Thu, 28 Dec 2000 00:00:00 +0200
Grammar Systems with Negated Conditions in their Cooperation Protocols https://lib.jucs.org/article/27740/ JUCS - Journal of Universal Computer Science 6(12): 1165-1184

DOI: 10.3217/jucs-006-12-1165

Authors: Henning Bordihn, Markus Holzer

Abstract: The investigation on Boolean operations on the stop conditions of derivation modes for cooperating distributed grammar systems is continued by considering the logical negation of such conditions. The focus is on the negation of the t-mode of derivation, where such non-t-components may stop rewriting only if they still have a production applicable to the current sentential form. In many cases, hybrid cooperating distributed grammar systems with non-t-components turn out to give new characterizations of the class of programmed context-free languages or recurrent programmed context-free languages, where the latter class coincides with the biologically motivated family of languages generated by ET0L systems with random context. Thus, the results presented in this paper can shed new light on some longstanding open problems in the theory of regulated rewriting.

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Research Article Thu, 28 Dec 2000 00:00:00 +0200
Uniquely Parsable Accepting Grammar Systems https://lib.jucs.org/article/27713/ JUCS - Journal of Universal Computer Science 6(9): 850-860

DOI: 10.3217/jucs-006-09-0850

Authors: Carlos Martín-Vide, Victor Mitrana

Abstract: We extend the restrictions which induce unique parsability in Chomsky grammars to accepting grammar systems. It is shown that the accepting power of global RC-uniquely parsable accepting grammar systems equals the computational power of deterministic pushdown automata. More computational power, keeping the parsability without backtracking, is observed for local accepting grammar systems satisfying the prefix condition. We discuss a simple recognition algorithm for these systems.

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Research Article Thu, 28 Sep 2000 00:00:00 +0300
Application of the FOREST Approach to the Light Control Case Study https://lib.jucs.org/article/27695/ JUCS - Journal of Universal Computer Science 6(7): 679-703

DOI: 10.3217/jucs-006-07-0679

Authors: Martin Kronenburg, Christian Peper

Abstract: Forest is a requirements engineering approach designed to support the creation of precise and intelligible problem specifications of reactive systems. It integrates a product model, a process model, and an editing tool. In this paper, we present the results of applying the Forest approach to the Light Control Case Study. This includes the presentation of excerpts of the resulting problem specification, as well as the discussion of the strengths and shortcomings of the Forest approach.

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Research Article Fri, 28 Jul 2000 00:00:00 +0300
Synchronization Expressions and Languages https://lib.jucs.org/article/27597/ JUCS - Journal of Universal Computer Science 5(9): 610-621

DOI: 10.3217/jucs-005-09-0610

Authors: Kai Salomaa, Sheng Yu

Abstract: Synchronization expressions (SEs) were originally developed as practical high-level constructs for specifying synchronization constraints between parallel processes. The family of synchronization languages was introduced to give a precise semantic description for synchronization expressions. In addition to its use for defining the meaning of SEs, the family of synchronization languages is interesting on its own from a formal languages point of view. We consider two variants of the definition of synchronization languages, and survey characterization results for the language families. Synchronization languages also provide us a systematic approach for the implementation and simplification of SEs.

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Research Article Tue, 28 Sep 1999 00:00:00 +0300
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
On Algebraicness of D0L Power Series https://lib.jucs.org/article/27531/ JUCS - Journal of Universal Computer Science 5(1): 11-19

DOI: 10.3217/jucs-005-01-0011

Authors: Juha Honkala

Abstract: We show that it is decidable whether or not a given D0L power series over a semiring A is A-algebraic in case A = Q+ or A = N. The proof relies heavily on the use of elementary morphisms in a power series framework and gives also a new method to decide whether or not a given D0L language is context-free.

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Research Article Thu, 28 Jan 1999 00:00:00 +0200
On N-Algebraic Parikh Slender Power Series https://lib.jucs.org/article/27416/ JUCS - Journal of Universal Computer Science 3(10): 1114-1120

DOI: 10.3217/jucs-003-10-1114

Authors: Juha Honkala

Abstract: In a recent paper we introduced Parikh slender languages and series as a generalization of slender languages defined and studied by Andrasiu, Dassow, Paun and Salomaa. Results concerning Parikh slender series can be applied in ambiguity proofs of context-free languages. In this paper an algorithm is presented for deciding whether or not a given N-algebraic series is Parikh slender.

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Research Article Tue, 28 Oct 1997 00:00:00 +0200
Remarks on Propagating Partition-Limited ETOL Systems https://lib.jucs.org/article/27303/ JUCS - Journal of Universal Computer Science 2(11): 745-755

DOI: 10.3217/jucs-002-11-0745

Authors: Henning Fernau

Abstract: In this paper, we sharpen the results of Gaeartner on the universality of partition-limited ET0L systems by showing that such deterministic systems characterize the recursively enumerable sets, and, furthermore, the propagating deterministic partition-limited ET0L systems characterize the programmed languages with appearance checking disallowing erasing productions. The main results of this paper have been announced in [10].

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Research Article Thu, 28 Nov 1996 00:00:00 +0200
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
On Images of Algebraic Series https://lib.jucs.org/article/27234/ JUCS - Journal of Universal Computer Science 2(4): 217-223

DOI: 10.3217/jucs-002-04-0217

Authors: Juha Honkala

Abstract: We show that it is decidable whether or not the set of coefficients of a given Q-algebraic sequence is finite. The same question is undecidable for Q-algebraic series. We consider also prime factors of algebraic series.

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Research Article Sun, 28 Apr 1996 00:00:00 +0300
Parikh Prime Words and GO-like Territories https://lib.jucs.org/article/27197/ JUCS - Journal of Universal Computer Science 1(12): 790-810

DOI: 10.3217/jucs-001-12-0790

Authors: Alexandru Mateescu, Gheorghe Paun, Grzegorz Rozenberg, Arto Salomaa

Abstract: An n-dimensional vector of natural numbers is said to be prime if the greatest common divisor of its components is one. A word is said to be Parikh prime if its Parikh vector is prime. The languages of Parikh prime and of Parikh non-prime words are investigated (they are neither semilinear nor slender, hence are not context-free or D0L languages, both of them can be generated by matrix grammars with appearance checking). Marking in the plane the points identified by prime (2-dimensional) vectors, interesting patterns of non-marked ("free") points appear (they are similar to the territories in the game of GO). The shape of such possible territories is investigated (with an exhaustive analysis of tro-, tetro-, pento- and hexominoes). Some open problems are formulated (both concerning the mentioned languages and the "GO territories theory"). 1.) Research supported by the Academy of Finland, project 11281, and the ESPRIT Basic Research Working Group ASMICS II.

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Research Article Thu, 28 Dec 1995 00:00:00 +0200
A Decision Method for the Unambiguity of Sets Defined by Number Systems https://lib.jucs.org/article/27163/ JUCS - Journal of Universal Computer Science 1(9): 652-657

DOI: 10.3217/jucs-001-09-0652

Authors: Juha Honkala

Abstract: We show that it is decidable, given a number system N, whether or not there is an unambiguous number system equivalent to N.

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Research Article Thu, 28 Sep 1995 00:00:00 +0200
Conditional Tabled Eco-Grammar Systems https://lib.jucs.org/article/27124/ JUCS - Journal of Universal Computer Science 1(5): 252-268

DOI: 10.3217/jucs-001-05-0252

Authors: Erzsebet Csuhaj-Varju, Gheorghe Paun, Arto Salomaa

Abstract: We investigate the generative capacity of the so-called conditional tabled eco-grammar systems (CTEG). They are a variant of ecogrammar systems, generative mechanisms recently introduced as models of the interplay between environment and agents in eco-systems. In particular, we compare the power of CTEG systems with that of programmed and of random context T0L systems and with that of ET0L systems. CTEG systems with one agent only (and without extended symbols) are found to be surprisingly powerful (they can generate non-ET0L languages). Representation theorems for ET0L and for recursively enumerable languages in terms of CTEG languages are also presented. 1.) Research supported by the Academy of Finland, Project 11281

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Research Article Sun, 28 May 1995 00:00:00 +0300
A Variant of Team Cooperation in Grammar Systems https://lib.jucs.org/article/27099/ JUCS - Journal of Universal Computer Science 1(2): 105-130

DOI: 10.3217/jucs-001-02-0105

Authors: Rudolf Freund, Gheorghe Paun

Abstract: We prove that grammar systems with (prescribed or free) teams (of constant size at least two or arbitrary size) working as long as they can do, characterize the family of languages generated by (context-free) matrix grammars with appearance checking; in this way, the results in [Paun, Rozenberg 1994] are completed and improved.

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Research Article Tue, 28 Feb 1995 00:00:00 +0200
Grammars Based on the Shuffle Operation https://lib.jucs.org/article/27088/ JUCS - Journal of Universal Computer Science 1(1): 67-82

DOI: 10.3217/jucs-001-01-0067

Authors: Gheorghe Paun, Grzegorz Rozenberg, Arto Salomaa

Abstract: We consider generative mechanisms producing languages by starting from a finite set of words and shuffling the current words with words in given sets, depending on certain conditions. Namely, regular and finite sets are given for controlling the shuffling: strings are shuffled only to strings in associated sets. Six classes of such grammars are considered, with the shuffling being done on a left most position, on a prefix, arbitrarily, globally, in parallel, or using a maximal selector. Most of the corresponding six families of languages, obtained for finite, respectively for regular selection, are found to be incomparable. The relations of these families with Chomsky language families are briefly investigated.

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