Behavioural notions for elementary net systems

We study the relationships between a number of behavioural notions that have arisen in the theory of distributed computing. In order to sharpen the under-standing of these relationships we apply the chosen behavioural notions to a basic net-theoretic model of distributed systems called elementary net systems. The behavioural notions that are considered here are trace languages, non-sequential processes, unfoldings and event structures. The relationships between these notions are brought out in the process of establishing that for each elementary net system, the trace language representation of its behaviour agrees in a strong way with the event structure representation of its behaviour. M. Nielsen received a Master of Science degree in mathematics and computer science in 1973, and a Ph.D. degree in computer science in 1976 both from Aarhus University, Denmark. He has held academic positions at Department of Computer Science, Aarhus University, Denmark since 1976, and was visiting researcher at Computer Science Department, University of Edinburgh, U.K., 1977–79, and Computer Laboratory, Cambridge University, U.K., 1986. His research interest is in the theory of distributed computing. Grzegorz Rozenberg received a master of engineering degree from the Department of Electronics (section computers) of the Technical University of Warsaw in 1964 and a Ph.D. in mathematics from the Institute of Mathematics of the Polish Academy of Science in 1968. He has held acdeemic positions at the Institute of Mathematics of the Polish Academy of Science, the Department of Mathematics of Utrecht University, the Department of Computer Science at SUNY at Buffalo, and the Department of Mathematics of the University of Antwerp. He is currently Professor at the Department of Computer Science of Leiden University and Adjoint Professor at the Department of Computer Science of the University of Colorado at Boulder. His research interests include formal languages and automata theory, theory of graph transformations, and theory of concurrent systems. He is currently President of the European Association for Theoretical Computer Science (EATCS). P.S. Thiagarajan received the Bachelor of Technology degree from the Indian Institute of Technology, Madras, India in 1970. He was awarded the Ph.D. degree by Rice University, Houston Texas, U.S.A, in 1973. He has been a Research Associate at the Massachusetts Institute of Technology, Cambridge a Staff Scientist at the Geosellschaft für Mathematik und Datenverarbeitung, St. Augustin, a Lektor at Århus University, Århus and an Associate Professor at the Institute of Mathematical Sciences, Madras. He is currently a Professor at the School of Mathematics, SPIC Science Foundation, Madras. He research intest is in the theory of distributed computing.     

P transducers

We introduce in this paper four classes of P transducers: arbitrary, initial, isolated arbitrary, isolated and initial. The first two classes are universal, they can compute the same word functions as Turing machines, the latter two are incomparable with finite state sequential transducers, generalized or not. We study the effect of the composition, and show that iteration increases the power of these latter classes, also leading to a new characterization of recursively enumerable languages. The “Sevilla carpet” of a computation is defined for P transducers, giving a representation of the control part for these P transducers. Gabriel Ciobanu, Ph.D.: He has graduated from the Faculty of Mathematics, “A.I.Cuza” University of Iasi, and received his Ph.D. from the same university. He is a senior researcher at the Institute of Computer Science of the Romanian Academy. He has wide-ranging interests in computing including distributed systems and concurrency, computational methods in biology, membrane computing, and theory of programming (semantics, formal methods, logics, verification). He has published around 90 papers in computer science and mathematics, a book on programming semantics and a book on network programming. He is a co-editor of three volumes. He has visited various universities in Europe, Asia, and North America, giving lectures and invited talks. His webpage is http://www.info.uaic.ro/gabriel Gheorghe Păun, Ph.D.: He has graduated from the Faculty of Mathematics, University of Bucharest, in 1974 and received his Ph.D. from the same university in 1977. Curently he works as senior researcher in the Institute of Mathematics of the Romanian Academy, as well as a Ramon y Cajal researcher in Sevilla University, Spain. He has repeatedly visited numerous universities in Europe, Asia, and North America. His main research areas are formal language theory and its applications, computational linguistics, DNA computing, and membrane computing (a research area initiated by him). He has published over 400 research papers (collaborating with many researchers worldwide), has lectured at over 100 universities, and gave numerous invited talks at recognized international conferences. He has published 11 books in mathematics and computer science, has edited about 30 collective volumes, and also published many popular science books and books on recreational mathematics (games). He is on the editorial boards of fourteen international journals in mathematics, computer science, and linguistics, and was/is involved in the program/steering/organizing commitees for many recognized conferences and workshops. In 1997 he was elected a member of the Romanian Academy. Gheorghe Ştefănescu, Ph.D.: He received his B.Sc./M.Sc./Ph.D. degrees in Computer Science from the University of Bucharest. Currently, he is a Professor of Computer Science at the University of Bucharest and a Senior Fellow at the National University of Singapore. Previously, he was a researcher at the Institute of Mathematics of the Romanian Academy and has held visiting positions in The Netherlands, Germany, and Japan. His current research focuses on formal methods in computer science, particularly on process and network algebras, formal methods for interactive, real-time, and object-oriented systems. Some of his results may be found in his book on “Network Algebra,” Springer, 2000.     

Combination of clock-state and clock-rate correction in fault-tolerant distributed systems

This paper proposes the integration of internal and external clock synchronization by a combination of a fault-tolerant distributed algorithm for clock state correction with a central algorithm for clock rate correction. By means of hardware and simulation experiments it is shown that this combination improves the precision of the global time base in a distributed single cluster system while reducing the need for high-quality oscillators. Simulation results have shown that the rate-correction algorithm contributes not only in the internal clock synchronization of a single cluster system, but it can be used for external clock synchronization of a multi-cluster system with a reference clock. Therefore, deployment of the rate-correction algorithm integrates internal and external clock synchronization in one mechanism. Experimental results show that a failure in the clock rate correction will not hinder the distributed fault-tolerant clock state synchronization algorithm, since the state correction operates independently from the rate correction. The paper introduces new algorithms and presents experimental results on the achieved improvements in the precision measured in a time-triggered system. Results of simulation experiments of the new algorithms in single-cluster and multi-cluster configurations are also presented. Hermann Kopetz (Fellow, IEEE) received the Ph.D. degree in physics ísub auspiciis praesidentis from the University of Vienna, Vienna, Austria, in 1968. He was Manager of the Computer Process Control Department at Voest Alpine, Linz, Austria, and Professor of Computer Process Control, Technical University of Berlin, Berlin, Germany. He is currently Professor of Real-Time Systems, Vienna University of Technology, Vienna, Austria, and a Visiting Professor at the University of California, Irvine, and the University of California, Santa Barbara. In 1993, he was offered a position as Director of the Max Planck Institute, Saarbrcken, Germany. Prof. Kopetz is the key architect of the Time-Triggered Architecture. Astrit Ademaj (IEEE member) received the Dipl-Ing. degree (1995) at the University of Prishtina, Kosova, and a doctoral degree (2003) in computer science from the Technical University of Vienna. He is currently working as Assistant Professor at the Technical University of Vienna and as a Visiting Lecturer at the University of Prishtina. His research interests are design and validation of communication systems for safety-critical and real-time applications. He is a member of the IEEE Computer Society. Alexander Hanzlik received a diploma (1995) and a doctoral degree (2004) in computer science from the Technical University of Vienna. From 1995 to 1998, he was concerned with voice communication system design for air traffic control for the Service de Navigation Aérienne (STNA). Since 1998, his focus is on embedded systems in the fields of telecommunication, automation and process control. Since 2001, Dr. Hanzlik is a member of the Real-Time Systems Group and works as a research assistant at the Technical University of Vienna. His main research activities deal with fault-tolerant clock synchronization in distributed systems and simulation. Currently, he is working on SIDERA, a simulation model for time-triggered, dependable real-time architectures.     

Temporal disjunctive logic programming

In this paper we introduce the logic programming languageDisjunctive Chronolog which combines the programming paradigms of temporal and disjunctive logic programming. Disjunctive Chronolog is capable of expressing dynamic behaviour as well as uncertainty, two notions that are very common in a variety of real systems. We present the minimal temporal model semantics and the fixpoint semantics for the new programming language and demonstrate their equivalence. We also show how proof procedures developed for disjunctive logic programs can be easily extended to apply to Disjunctive Chronolog programs. Manolis Gergatsoulis, Ph.D.: He received his B.Sc. in Physics in 1983, the M.Sc. and the Ph.D. degrees in Computer Science in 1986 and 1995 respectively all from the University of Athens, Greece. Since 1996 he is a Research Associate in the Institute of Informatics and Telecommunications, NCSR ‘Demokritos’, Athens. His research interests include logic and temporal programming, program transformations and synthesis, as well as theory of programming languages. Panagiotis Rondogiannis, Ph.D.: He received his B.Sc. from the Department of Computer Engineering and Informatics, University of Patras, Greece, in 1989, and his M.Sc. and Ph.D. from the Department of Computer Science, University of Victoria, Canada, in 1991 and 1994 respectively. From 1995 to 1996 he served in the Greek army. From 1996 to 1997 he was a visiting professor in the Department of Computer Science, University of Ioannina, Greece, and since 1997 he is a Lecturer in the same Department. In January 2000 he was elected Assistant Professor in the Department of Informatics at the University of Athens. His research interests include functional, logic and temporal programming, as well as theory of programming languages. Themis Panayiotopoulos, Ph.D.: He received his Diploma on Electrical Engineering from the Department of Electrical Engineering, National Technical Univesity of Athens, in 1984, and his Ph.D. on Artificial Intelligence from the above mentioned department in 1989. From 1991 to 1994 he was a visiting professor at the Department of Mathematics, University of the Aegean, Samos, Greece and a Research Associate at the Institute of Informatics and Telecommunications of “Democritos” National Research Center. Since 1995 he is an Assistant Prof. at the Department of Computer Science, University of Piraeus. His research interests include temporal programming, logic programming, expert systems and intelligent agent architectures.     

Constructive negation and constraint logic programming with sets

The aim of this paper is to extend theConstructive Negation technique to the case ofCLP(SεT), a Constraint Logic Programming (CLP) language based on hereditarily (and hybrid) finite sets. The challenging aspects of the problem originate from the fact that the structure on whichCLP(SεT) is based is notadmissible closed, and this does not allow to reuse the results presented in the literature concerning the relationships betweenCLP and constructive negation. We propose a new constraint satisfaction algorithm, capable of correctly handling constructive negation for large classes ofCLP(SεT) programs; we also provide a syntactic characterization of such classes of programs. The resulting algorithm provides a novel constraint simplification procedure to handle constructive negation, suitable to theories where unification admits multiple most general unifiers. We also show, using a general result, that it is impossible to construct an interpreter forCLP(SεT) with constructive negation which is guaranteed to work for any arbitrary program; we identify classes of programs for which the implementation of the constructive negation technique is feasible. Agostino Dovier, Ph.D.: He is a researcher in the Department of Science and Technology at the University of Verona, Italy. He obtained his master degree in Computer Science from the University of Udine, Italy, in 1991 and his Ph.D. in Computer Science from the University of Pisa, Italy, in 1996. His research interests are in Programming Languages and Constraints over complex domains, such as Sets and Multisets. He has published over 20 research papers in International Journals and Conferences. He is teaching a course entitled “Special Languages and Techniques for Programming” at the University of Verona. Enrico Pontelli, Ph.D.: He is an Assistant Professor in the Department of Computer Science at the New Mexico State University. He obtained his Laurea degree from the University of Udine (Italy) in 1991, his Master degree from the University of Houston in 1992, and his Ph.D. degree from New Mexico State University in 1997. His research interests are in Programming Languages, Parallel Processing, and Constraint Programming. He has published over 50 papers and served on the program committees of different conferences. He is presently the Associate Director of the Laboratory for Logic, Databases, and Advanced Programming. Gianfranco Rossi, Ph.D.: He received his degree in Computer Science from the University of Pisa in 1979. From 1981 to 1983 he was employed at Intecs Co. System House in Pisa. From November 1983 to February 1989 he was a researcher at the Dipartimento di Informatica of the University of Turin. Since March 1989 he is an Associate Professor of Computer Science, currently with the University of Parma. He is the author of several papers dealing mainly with programming languages, in particular logic programming languages and Prolog, and extended unification algorithms. His current research interests are (logic) programming languages with sets and set unification algorithms.     

P systems with local graph productions

P systems (membrane systems) of various types so far mainly have been considered as computing devices working on multisets or strings. In this paper we investigate P systems with local graph productions generating weakly connected directed graphs. At least when equipped with a priority relation on the rules, such P systems can generate any recursively enumerable language of weakly connected directed graphs with only one membrane. Rudolf Freund, Ph.D.: He holds a master and doctor degree in computer science and a master degree in mathematics and physics. Since 1995 he is Associate Professor at the Vienna University of Technology in Austria. His research interests include array and graph grammars, regulated rewriting, infinite words, syntactic pattern recognition, neural networks, and especially models and systems for biological computing. In these fields, he is author or co-author of more than ninety scientific papers. Marion Oswald, Ph.D.: She received her master and doctor degree in computer science from the Vienna University of Technology, Austria, in 2001 and 2003, respectively. Her research interests include but are not limited to artificial life as well as models and systems for biological computing, in which fields she is author or co-author of more than fifteen scientific papers.     

Polynomial-time learning of elementary formal systems

An elementary formal system (EFS) is a logic program consisting of definite clauses whose arguments have patterns instead of first-order terms. We investigate EFSs for polynomial-time PAC-learnability. A definite clause of an EFS is hereditary if every pattern in the body is a subword of a pattern in the head. With this new notion, we show that H-EFS(m, k, t, r) is polynomial-time learnable, which is the class of languages definable by EFSs consisting of at mostm hereditary definite clauses with predicate symbols of arity at mostr, wherek andt bound the number of variable occurrences in the head and the number of atoms in the body, respectively. The class defined by all finite unions of EFSs in H-EFS(m, k, t, r) is also polynomial-time learnable. We also show an interesting series ofNC-learnable classes of EFSs. As hardness results, the class of regular pattern languages is shown not polynomial-time learnable unlessRP=NP. Furthermore, the related problem of deciding whether there is a common subsequence which is consistent with given positive and negative examples is shownNP-complete. Satoru Miyano, Dr. Sci.: He is a Professor in Human Genome Center at the University of Tokyo. He obtained B.S. in 1977, M.S. in 1979, and Dr. Sci. degree all in Mathematics from Kyushu University. His current interests include bioinformatics, discovery science, computational complexity, computational learning. He has been organizing Genome Informatics Workshop Series since 1996 and has served for the chair/member of the program committee of many conferences in the area of Computer Science and Bioinformatics. He is on the Editorial Board of Theoretical Computer Science and the Chief Editor of Genome Informatics Series. Ayumi Shinohara, Dr. Sci.: He is an Associate Professor in the Department of Informatics at Kyushu University. He obtained B.S. in 1988 in Mathematics, M.S. in 1990 in Information Systems, and Dr. Sci. degree in 1994 all from Kyushu University. His current interests include discovery science, bioinformatics, and pattern matching algorithms. Takeshi Shinohara, Dr. Sci.: He is a Professor in the Department of Artificial Intelligence at Kyushu Institute of Technology. He obtained his B.S. in Mathematics from Kyoto University in 1980, and his Dr. Sci. degree from Kyushu University in 1986. His research interests are in Computational/Algorithmic Learning Theory, Information Retrieval, and Approximate Retrieval of Multimedia Data.     

Taut-String Algorithm and Regularization Programs with <Emphasis Type="Italic">G</Emphasis>-Norm Data Fit

In this paper we derive a unified framework for the taut-string algorithm and regularization with G-norm data fit. The G-norm data fit criterion (popularized in image processing by Y. Meyer) has been paid considerable interest in regularization models for pattern recognition. The first numerical work based on G-norm data fit has been proposed by Osher and Vese. The taut-string algorithm has been developed in statistics (Mammen and van de Geer and Davies and Kovac) for denoising of one dimensional sample data of a discontinuous function. Recently Hinterberger et al. proposed an extension of the taut-string algorithm to higher dimensional data by introducing the concept of tube methods. Here we highlight common features between regularization programs with a G-norm data fit term and taut-string algorithms (respectively tube methods). This links the areas of statistics, regularization theory, and image processing. Otmar Scherzer received his Ph.D. in Mathematics from the University of Linz, Austria, in 1990. Till 1999 he has been at the Industrial Mathematics Institute at the University of Linz. From 1999–2000 he visited the University of Munich (Germany) and from 2000–2001 he was Professor at the University of Bayreuth (Germany). Since 2001 he is Professor at the Department of Computer Science at the University of Innsbruck (Austria). From 1995 to 1996 he had an Erwin Schrödinger Scholarship of the Austrian Science Foundation (FWF) for visiting Texas A&M University and the University of Delaware (USA). Otmar Scherzer received the Award of the Austrian Mathematical Society (1998) and the START-price of the FWF in (1999). He is in the editorial board of Numerical Functional Analysis and Optimization and Inverse Problems. His research interest include image processing and inverse problems.This revised version was published online in June 2005 with correction to CoverDate     

A portable approach to dynamic optimization in run-time specialization

This paper proposes arun-time bytecode specialization (BCS) technique that analyzes programs and generates specialized programs at run-time in an intermediate language. By using an intermediate language for code generation, a back-end system canoptimize the specialized programs after specialization. The system uses Java virtual machine language (JVML) as the intermediate language, which allows the system to easily achieve practicalportability and to use existing sophisticated just-in-time (JIT) compilers as its back-end. The binding-time analysis algorithm is based on a type system, and covers a non-object-oriented subset of JVML. The specializer generates programs on a per-instruction basis, and can performmethod inlining at run-time. Our performance measurements show that a non-trivial application program specialized at run-time by BCS runs approximately 3–4 times faster than the unspecialized one. Despite the large overhead of JIT compilation of specialized code, we observed that the overall performance of the application can be improved. This paper is an extended version of “A Portable Approach to Generating Optimized Specialized Code”, inProceedings of Second Symposium on Programs as Data Objects (PADO-II), Lecture Notes in Computer Science, vol. 2053, pp. 138–154, Aarhus, Denmark, May 2001.²³) Hidehiko Masuhara, D.Sc.: He is an Assistant Professor at Department of Graphics and Computer Science, Graduate School of Arts and Sciences, University of Tokyo. He received his B.S., M.S. and D.Sc. degrees from Department of Information Science, University of Tokyo in 1992, 1994, and 1999, respectively. His research interests are in programming languages, especially in mechanisms to support flexible and efficient computation such as dynamic optimization and reflection. He received the best-paper award from Information Processing Society of Japan in 1996. Akinori Yonezawa, Ph.D.: He is a Professor of computer science at Department of Computer Science, University of Tokyo. He received Ph.D. in Computer Science from the Massachusetts Institute of Technology in 1977. His current major research interests are in the areas of concurrent/parallel computation models, programming languages, object-oriented computing, and distributed computing. He is the designer of an object-oriented concurrent language ABCL/1 and the editor of several books and served as an associate editor of ACM Transaction of Programming Languages and Systems (TOPLAS). Since 1998, he has been an ACM Fellow.     

Life sciences grid in EUROGRID and GRIP projects

In this paper we describe deployment of most important life sciences applications on the grid. The build grid is heterogenous and consist of systems of different architecture as well as operating systems and various middleware. We have used UNICORE infrastructure as framework for development dedicated user interface to the number of existing computational chemistry codes and molecular biology databases. Developed solution allows for access to the resources provided with UNICORE as well as Globus with exactly the same interface which gives access to the general grid functionality such as single login, job submission and control mechanism. Jarosław Wypychowski: He is a student at the Faculty of Mathematics and Computer Science, Warsaw University, Poland. He is involved in the development of grid tools. He has been working as programmer in the private company. Jarosław Pytliński, M.Sc.: He received his M.Sc. in 2002 from Department of Mathematic and Computer Science of Nicolaus Copernicus University in Torun. His thesis on “Quantum Chemistry Computations in Grid Environment” was distincted in XIX Polish Contest for the best M.Sc. Thesis of Computer Science. He also worked in Laboratory of High Performance Systems at UCI, Torun. His interests are Artificial Intelligence and GRID technology. Łukasz Skorwider, M.Sc.: He is programmer in the private pharmaceutical company. He obtained M.Sc. degree from the Faculty of Mathematics and Computer Science N. Copernicus University. As graduate student he was involved in the development of grid tools for drug design. His private and professional interest is Internet technology. Mirosław Nazaruk, M.Sc.: He is a senior computer and network administrator at ICM Warsaw University. He provides professional support for the users of the high performance facilities located at the ICM. He obtained M.Sc. in Computer Science from Warsaw University in 1991. Before joining ICM, he was a member of technical staff at Institute of Applied Mathematics, Warsaw University. Krzysztof Benedyczak: He is a student at the Faculty of Mathematics and Computer Science, N. Copernicus University, Torun, Poland. He is involved in the development of grid tools. Michał Wroński: He is a student at the Faculty of Mathematics and Computer Science, N. Copernicus University, Torun, Poland. He is involved in the development of grid tools. Piotr Bała, Ph.D.: He is an adiunkt at Faculty of Mathematics and Computer Science N. Copernicus University, Torun, Poland, and tightly cooperates with ICM, Warsaw University. He obtained Ph.D. in Physics in 1993 in Institute of Physics, N. Copernicus University and in 2000 habilitation in physics. From 2001 he was appointed director of Laboratory of Parallel and Distributed Processing at Faculty of Mathematics, N. Copernicus University. His main research interest is development and application of Quantum-Classical Molecular Dynamics and Approximated Valence Bond method to study of enzymatic reactions in biological systems. In the last few years, he has been involved in development of parallel and grid tools for large scale scientific applications.     

Circular attribute grammars with remote attribute references and their evaluators

Attribute grammars (AGs) are a suitable formalism for the development of language processing systems. However, for languages including unrestricted labeled jumps, such as “goto” in C, the optimizers in compilers are difficult to write in AGs. This is due to two problems that few previous researchers could deal with simultaneously, i.e., references of attribute values on distant nodes and circularity in attribute dependency. This paper proposescircular remote attribute grammars (CRAGs), an extension of AGs that allows (1) direct relations between two distant attribute instances through pointers referring to other nodes in the derivation tree, and (2) circular dependencies, under certain conditions including those that arise from remote references. This extension gives AG programmers a natural means of describing language processors and programming environments for languages that include any type of jump structure. We also show a method of constructing an efficient evaluator for CRAGs called amostly static evaluator. The performance of the proposed evaluator has been measured and compared with dynamic and static evaluators. Akira Sasaki: He is a research fellow of the Advanced Clinical Research Center in the Institute of Medical Science at the University of Tokyo. He received his BSc and MSc from Tokyo Institute of Technology, Japan, in 1994 and 1996, respectively. His research interests include programming languages, programming language processors and programming environments, especially compiler compilers, attribute grammars and systematic debugging. He is a member of the Japan Society for Software Science and Technology. Masataka Sassa, D.Sc.: He is Professor of Computer Science at Tokyo Institute of Technology. He received his BSc, MSc and DSc from the University of Tokyo, Japan, in 1970, 1972 and 1978, respectively. His research interests include programming languages, programming language processors and programming environments, currently he is focusing on compiler optimization, compiler infrastructure, attribute grammars and systematic debugging. He is a member of the ACM, IEEE Computer Society, Japan Society for Software Science and Technology, and Information Processing Society of Japan.     

Blackboard relations in the μLog coordination model

This paper describescoordination relations, that are relations that induce the presence or absence of data on some dataspaces from the presence or absence of other data on other dataspaces. To that end we build upon previous work on the μLog model and show that the coordination relations can be easily incorporated in it. This is achieved, on the one hand, by means of novel auxiliary operations, not classically used in Linda-like languages, and, on the other hand, by a translation technique reducing the extended μLog model to the core model augmented with the auxiliary operations. Among the most significant ones are multiple read and get operations on a blackboard, readall and getall operations, and tests for the absence of data on blackboards. Although simple, the form of coordination relations we propose is quite powerful as evidenced by a few examples including relations coming from the object-oriented paradigm such as inheritance relations. Jean-Marie Jacquet, Ph.D.: He is Professor at the Institute of Informatics at the University of Namur, Belgium, and, at an honorary title, Research Associate of the Belgian National Fund for Scientific Research. He obtained a Master in Mathematics from the University of Liège in 1982, a Master in Computer Science from the University of Namur in 1984 and a Ph.D. in Computer Science from the University of Namur in 1989. His research interest are in Programming Languages and Coordination models. He has served as a reviewer and program committee member of several conferences. Koen de Bosschere, Ph.D.: He holds the degree of master of Science in Engineering of the Ghent University, and a Ph.D. from the same University. He is currently research associate with the Fund for Scientific Research — Flanders and senior lecturer at the Ghent University, where he teaches courses on computer architecture, operating systems and declarative programming languages. His research interests are coordination in parallel logic programming, computer architecture and systems software.     

Nonmetrical distances on the hexagonal grid using neighborhood sequences

the theory of neighborhood sequences is applicable in many image-processing algorithms. The theory is well known and has been analyzed for square and cubic grids. In this paper we consider a hexagonal grid. We use three kinds of neighbors; therefore, the neighborhood sequences allow more flexibility in the hexagonal plane than in the square one. Some interesting properties of these distances are presented, such as nonsymmetrical distances and that some of the distances do not meet the triangular inequality. In this paper we present sufficient and necessary conditions for neighborhood sequences define symmetric and/or triangular distance functions. Both metrical and nonmetrical distances are described on the hexagonal grid. The text was submitted by the author in English. Benedek Norbert Nagy has born in 1973 in Hungary. He graduated from the University of Debrecen (before 2000, Lajos Kossuth University) in Hungary as a physicist, programmer mathematician, philosopher, logician, computer scientist, and general and applied linguist in 1996, 1997, 1998, 1999, and 2000, respectively. In 2004 he received his PhD in Mathematics and Computer Science in the same university and graduated summa cum laude; his dissertation bore the title “Neighborhood Sequences in Different Grids.” He is currently an assistant professor in the Department of Computer Science, University of Debrecen. He is a member of the Research Group on Mathematical Linguistics at Rovira i Virgili University, Tarragona, Spain. His research interest consists of various fields, mostly in discrete mathematics and theoretical computer science. He has published papers on logical puzzles and graphs, as well as several on theoretical image processing and pattern analysis. He also has had results in the theory of formal languages and automata. By the beginning of 2005, he had published 15 journal papers and more than 20 papers in conference proceedings. He is a member of the International Association for Pattern Recognition, the John von Neumann Computer Society, the Artificial Intelligence and Pattern Recognition Society, and the Janos Bolyai Mathematical Society. He has won several scientific competitions and prizes. His most recent prize was the Prize of Foundation Laszlo Patai in 2004.     

An LMI approach to robust reduced-order H ∞ filter design for polytopic uncertain systems

This paper proposes a method for robust reduced-order H _∞ filter design for polytopic uncertain systems, using linear matrix inequalities (LMIs). Sufficient LMI conditions for both robust full- and reduced-order H _∞ filter design are derived. Convex optimization problems are formulated and solved to obtain optimal H _∞ filters by using the resulting LMI conditions. The resulting conditions do not involve any non-convex rank constraints, and thus the proposed method for H _∞ filter design guarantees global optimum solutions. Numerical examples are presented to show the effectiveness of the proposed method. Recommended by Editorial Board member Huanshui Zhang under the direction of Editor Young Il Lee. This work was supported by the Brain Korea 21 Project and the Basic Research Program of the Korea Science and Engineering Foundation under grant R01-2006-000-11373-0. Hyoun-Chul Choi received the B.S., M.S., and Ph.D. degrees in Control and Instrumentation Engineering from Ajou University, Suwon, Korea, in 1995, 1997, and 2006, respectively. He was a Visiting Researcher at Griffith University, Brisbane, Australia, from 2001 to 2002, and a Postdoctoral researcher at Ajou University, Suwon, Korea, from 2006 to 2007. Since 2008, he has been with ASRI, School of Electrical Engineering and Computer Science, Seoul National University, Seoul, Korea, where he is currently a Postdoctoral Researcher. His research interests include LMI-based control, optimal and robust control, network-based control, and mechatronics. Dongkyoung Chwa received the B.S. and M.S. degrees from the Department of Control and Instrumentation Engineering in 1995 and 1997, respectively, and the Ph.D. degree from the School of Electrical and Computer Engineering in 2001, all from Seoul National University, Seoul, Korea. From 2001 to 2003, he was a Postdoctoral Researcher with Seoul National University. In 2003, he was a Visiting Research Fellow at The University of New South Wales, Australian Defence Force Academy, and was the Honorary Visiting Academic at the University of Melbourne, Melbourne, Australia. In 2004, he was a BK21 Assistant Professor with Seoul National University. Since 2005, he has been an Assistant Professor with the Department of Electrical and Computer Engineering, Ajou University, Suwon, Korea. His research interests are nonlinear, robust, and adaptive control theories and their applications to the robotics, underactuated systems including wheeled mobile robots, underactuated ships, cranes, and guidance and control of flight systems. Suk-Kyo Hong received the B.S., M.S., and Ph.D. degrees in Electrical Engineering from Seoul National University, Seoul, Korea, in 1971, 1973, and 1981, respectively. His major graduate research works were centered on speed control of induction motors. He was an Exchange Professor at Rensselaer Polytechnic Institute, Troy, NY, from 1982 to 1983, and at the Institut National de Recherche en Informatique et en Automatique, France, from 1988 to 1989. He has been with the faculty of the Department of Electrical and Computer Engineering, Ajou University, Suwon, Korea, since 1976, and was a Visiting Professor at Griffith University, Australia, in 2001 and 2002. His current research interests include robust robot control, microprocessor applications, factory automation, and computer integrated manufacturing.     

An Interactive Learning Algorithm for Acquisition of Concepts Represented as CFL

In this paper,an interactive learning algorithm of context-frmm language is presented.This algorithm is designed especially for system SAQ,which is a system for formal secification acquisition and verification.As the kernel of concept acquisition subsystem(SAQ/CL)of SAQ,the algorithm has been implemented on SUN SPARC workstation.The grammar to be obtained can represent sentence structure naturally.     

Test minimization for human-computer interaction

This paper introduces a model-based approach for minimization of test sets to validate the interaction of human-computer systems. The novelty of the approach is twofold: (i) Test cases generated and selected holistically cover both the behavioral model and the complementary, fault model of the system under test (SUT). (ii) Methods known from state-based conformance testing and graph theory are extended to construct efficient, heuristic search-based algorithms for minimizing the test sets that are constructed in step (i), considering also structural features. Experience shows that the approach can help to considerably save test costs, up to 60% Fevzi Belli received the M.S., Ph.D., and Habilitation degrees in electrical engineering and computer science from the Berlin Technical University. He is presently a Professor of Software Engineering in the Faculty of Computer Science, Electrical Engineering and Mathematics, University of Paderborn, Paderborn, Germany. Prior to this, he headed several projects at a software house in Munich, was a Professor of Computing Science at the Hochschule Bremerhaven and a faculty member of the University of Maryland, European Division. He chaired several international conferences, e.g., ISSRE 1998 and is author and co-author of more than 100 papers published in scientific journals and conference proceedings. His research interests are in testing/fault tolerance/reliability of software and programming techniques. Christof J. Budnik received the MS degree in electrical engineering and computer science in 2001 from the University of Paderborn. In 2002, he joined the Department of Computer Science, Electrical Engineering and Mathematics at the same University where he is currently a faculty member. His research interests are in the areas of software quality, testing of interactive systems and safety-critical user interfaces.     

Efficient discovery of optimal word-association patterns in large text databases

We study efficient discovery of proximity word-association patterns, defined by a sequence of strings and a proximity gap, from a collection of texts with the positive and the negative labels. We present an algorithm that finds alld-stringsk-proximity word-association patterns that maximize the number of texts whose matching agree with their labels. It runs in expected time complexityO(k ^d−1n log ^d n) and spaceO(k ^d−1n) with the total lengthn of texts, if texts are uniformly random strings. We also show that the problem to find one of the best word-association patterns with arbitrarily many strings in MAX SNP-hard. Shinichi Shimozono, Ph.D.: He is an Associate Professor of the Department of Artificial Intelligence at Kyushu Institute of Technology Iizuka, Japan. He obtained the B.S. degree in Physics from Kyushu University, awarded M.S. degree from Graduate School of Information Science in Kyushu University, and his Dr. Sci. degree in 1996 from Kyushu University. His research interests are primarily in the design and analysis of algorithms for intractable problems. Hiroki Arimura, Ph.D.: He is an Associate Professor of the Department of Informatics at Kyushu University, Fukuoka, Japan. He is also a researcher with Precursory Research for Embryonic Science and Technology, Japan Science and Technology Corporation (JST) since 1999. He received the B.S. degree in 1988 in Physics, the M.S. degree in 1979 and the Dr.Sci. degree in 1994 in Information Systems from Kyushu University. His research interests include data mining, computational learning theory, and inductive logic programming. Setsuo Arikawa, Ph.D.: He is a Professor of the Department of Informatics and the Director of University Library at Kyushu University, Fukuoka, Japan. He received the B.S. degree in 1964, the M.S. degree in 1966 and the Dr.Sci. degree in 1969 all in Mathematics from Kyushu University. His research interests include Discovery Science, Algorithmic Learning Theory, Logic and Inference/Reasoning in AI, Pattern Matching Algorithms and Library Science. He is the principal investigator of the Discovery Science Project sponsored by the Grant-in Aid for Scientific Research on Priority Area from the Ministry of ESSC, Japan.     

Minimizing evolution-communication P systems and automata

Evolution-communication P systems are a variant of P systems allowing both rewriting rules and symport/antiport rules, thus having separated the rewriting and the communication. The purpose of this paper is to solve an open problem stated in Reference,¹⁾ namely generating the family of Turing computable sets of vectors of natural numbers instead of the family of Turing computable sets of natural numbers. The same construction also reduces the 3-membrane non-cooperative case and the 2-membrane 1-catalyst case to the 2-membrane non-cooperative case. Also, EC P automata are introduced and it is proved that 2-membrane EC P automata with a promoter can accept all recursively enumerable languages. Finally, a definition of an extended system is given, and its universality is proved using the rules of more restricted types. Artiom Alhazov: He has graduated from Mathematics and Computer Science, State University of Moldova in 2001, and is currently a Ph.D. student in Chişinăm, Moldova, and Tarragona, Spain. He has won prizes at 3 National Olympiads in Informatics and in Mathematics (1995 and 1996), participated at 8th International Olympiad in Informatics (Veszprem, Hungary, 1996). He has experience in programming and teaching, and has published 18 papers, mostly in Membrane Computing. His interests are Origami, Mathematics, Programming, Theoretical Computer Science, Formal Linguistics and Biocomputing.     

Results on catalytic and evolution-communication P systems

In this paper we give several improved universality results for two important classes of P systems: P systems with catalysts and evolution-communication P systems. First, the result from Reference,¹⁴⁾ stating that six catalysts ensure the universality, has been improved in two ways: using bistable catalysts and using moving catalysts. Specifically, the universality can be reached with one bistable catalyst and 2 usual catalysts (using five membranes), as well as with one moving catalyst and three membranes, or with two moving catalysts and only two membranes. The second part of the paper deals with evolution-communication P systems, and we also give improved universality results for this type of systems, in terms of the weight of symport/antiport rules, number of membranes, or number of catalysts. Shankara Narayanan Krishna: She is an Assistant Professor in Dept. Computer Science & Engg, IIT Bombay, India. Her research interests are Natural Computing and Formal Methods. Andrei Paun, Ph.D.: He obtained his bachelor degree in Mathematics and Computer Science from the University of Bucharest, Romania. He obtaind his Ph.D. degree in Computer Science, at University of Western Ontario, Canada, under the supervision of Prof. Dr. Sheng Yu, with the thesis “Unconventional Models of Computation: DNA and Membrane Computing”. After graduation he received a postdoctoral felloship from NSERC, Canada and after six months he accepted an assistant professor position in US at Louisiana Tech University.     

On Semismooth Newton’s Methods for Total Variation Minimization

In [2], Chambolle proposed an algorithm for minimizing the total variation of an image. In this short note, based on the theory on semismooth operators, we study semismooth Newton’s methods for total variation minimization. The convergence and numerical results are also presented to show the effectiveness of the proposed algorithms. The research of this author is supported in part by Hong Kong Research Grants Council Grant Nos. 7035/04P and 7035/05P, and HKBU FRGs. The research of this author is supported in part by the Research Grant Council of Hong Kong. This work was started while the author was visiting Department of Applied Mathematics, The Hong Kong Polytechnic University. The research of this author is supported in part by The Hong Kong Polytechnic University Postdoctoral Fellowship Scheme and the National Science Foundation of China (No. 60572114). Michael Ng is a Professor in the Department of Mathematics at the Hong Kong Baptist University. As an applied mathematician, Michael’s main research areas include Bioinformatics, Data Mining, Operations Research and Scientific Computing. Michael has published and edited 5 books, published more than 140 journal papers. He is the principal editor of the Journal of Computational and Applied Mathematics, and the associate editor of SIAM Journal on Scientific Computing. Liqun Qi received his B.S. in Computational Mathematics at Tsinghua University in 1968, his M.S, and Ph.D. degree in Computer Sciences at University of Wisconsin-Madison in 1981 and 1984, respectively. Professor Qi has taught in Tsinghua University, China, University of Wisconsin-Madison, USA, University of New South Wales, Australia, and The Hong Kong Polytechnic University. He is now Chair Professor of Applied Mathematics at The Hong Kong Polytechnic University. Professor Qi has published more than 140 research papers in international journals. He established the superlinear and quadratic convergence theory of the generalized Newton method, and played a principal role in the development of reformulation methods in optimization. Professor Qi’s research work has been cited by the researchers around the world. According to the authoritative citation database ISIHighlyCited.com, he is one of the world’s most highly cited 300 mathematicians during the period from 1981 to 1999. Yu-Fei Yang received the B.Sc., M.S. and Ph.D. degrees in mathematics from Hunan University, P. R. China, in 1987, 1994 and 1999, respectively. From 1999 to 2001, he stayed at the University of New South Wales, Australia as visiting fellow. From 2002 to 2005, he held research associate and postdoctoral fellowship positions at the Hong Kong Polytechnic University. He is currently professor in the College of Mathematics and Econometrics, at Hunan University, P. R. China. His research interests includes optimization theory and methods, and partial differential equations with applications to image analysis. Yu-Mei Huang received her M.Sc. in Computer science from Lanzhou University in 2000. She is now pursuing her doctoral studies in computational mathematics in Hong Kong Baptist University. Her research interests are in image processing and numerical linear algebra.