Fundamenta Informaticae - Volume 72, issue 1-3

Authors: Nowak, Agnieszka | Wakulicz-Deja, Alicja | Bachliński, Sebastian

Article Type: Research Article

Abstract: Optimization of the speech recognition process is aiming at achieving short time of classification (speech to text system), while preserving the content of speech signal description, and all necessary details of speech signal in considered application. The goal of parametrization of the human's speech is to eliminate of those physical features of speech signal, that do not bring any useful information (e.g., frequency of laryngeal tone, timbre of voice). The purpose of the parametrization of a …speech signal is to minimize the volume of information that is to be analyzed. Our experiments suggest that using the cluster analysis method with agglomerative hierarchical technique is very helpful in finding relationships between speech phones. It lets us accelerate the process of speech recognition, simply because it is not necessary to analyze each phone separately and comparing it with an unclassified object. This principle has been carried to hidden Markov models. To organize those models we use the cluster analysis method with hierarchical techniques. Each model represents a single sequence of speech (probably the phone sequence). At the "top" of the structure we have models of phones in the most general context. When we go thru this structure to the bottom, there are models of phones in particular context. By the context we understand the juxtaposition the different phones. Show more

Citation: Fundamenta Informaticae, vol. 72, no. 1-3, pp. 283-293, 2006

Authors: Nguyen, Trung Thanh | Willis, Claire P. | Paddon, Derek J. | Nguyen, Sinh Hoa | Nguyen, Hung Son

Article Type: Research Article

Abstract: Sunspots are the subject of interest to many astronomers and solar physicists. Sunspot observation, analysis and classification form an important part of furthering the knowledge about the Sun. Sunspot classification is a manual and very labor intensive process that could be automated if successfully learned by a machine. This paper presents machine learning approaches to the problem of sunspot classification. The classification scheme attempted was the seven-class Modified Zurich scheme [18]. The data was obtained by …processing NASA SOHO/MDI satellite images to extract individual sunspots and their attributes. A series of experiments were performed on the training dataset with an aim of learning sunspot classification and improving prediction accuracy. The experiments involved using decision trees, rough sets, hierarchical clustering and layered learning methods. Sunspots were characterized by their visual properties like size, shape, positions, and were manually classified by comparing extracted sunspots with corresponding active region maps (ARMaps) from the Mees Observatory at the Institute for Astronomy, University of Hawaii. Show more

Keywords: sunspot classification, layered learning, rough sets, machine learning

Citation: Fundamenta Informaticae, vol. 72, no. 1-3, pp. 295-309, 2006

Authors: Ochmański, Edward | Pieckowska, Joanna

Article Type: Research Article

Abstract: Trace nets are a generalization of elementary nets, proposed by Badouel and Darondeau. They admit phenomena, unknown in traditional nets. For instance, in trace nets does not hold the "diamond property". For this reason, we propose a more precise definition of conflict, applicable to trace nets, and study occurrences of conflicts and existence of conflict-free runs in such nets. Main result of the paper says that any just computation in a trace net, starting from a …conflict state, contains a conflict step. This result allows to construct an algorithm, selecting only conflict-free just computations from among all computations of a given net. All results of the paper hold for elementary nets, as they are a subclass of trace nets. Show more

Keywords: Petri nets, trace nets, conflicts

Citation: Fundamenta Informaticae, vol. 72, no. 1-3, pp. 311-321, 2006

Authors: Ochmański, Edward | Stawikowska, Krystyna

Article Type: Research Article

Abstract: The paper deals with star-free languages in free monoids and trace monoids. We introduce the notion of star-free star, fundamental for this paper, and show that the classes of star-free languages and star-free star languages coincide. Then, using this result, we obtain a general characterization of star-free trace languages, containing a result of Guaiana/Restivo/Salemi (star-free=aperiodic in trace monoids), originally proved in a more involved, combinatorial way.

Keywords: star-free languages, traces languages

Citation: Fundamenta Informaticae, vol. 72, no. 1-3, pp. 323-331, 2006

Authors: Redziejowski, Roman R.

Article Type: Research Article

Abstract: The notion of an associative omega-product is applied to processes. Processes are one of the ways to represent behavior of Petri nets. They have been studied for some years as an alternative to traces and dependence graphs. One advantage of processes, as compared to traces, is a very simple way to define infinite concatenation. We take a closer look at this operation, and show that it is a free associative omega-product of finite processes. Its associativity …simplifies some arguments about infinite concatenation, as illustrated by the proof of interleaving theorem. Show more

Citation: Fundamenta Informaticae, vol. 72, no. 1-3, pp. 333-345, 2006

Authors: Shilov, N.V. | Garanina, N.O. | Choe, K.-M.

Article Type: Research Article

Abstract: We present (update+abstraction) algorithm for model checking a fusion of Computation Tree Logic and Propositional Logic of Knowledge in systems with the perfect recall synchronous semantics. It has been already known that the problem is decidable with a non-elementary lower bound. The decidability follows from interpretation of the problem in a so-called Chain Logic and then in the Second Order Logic of Monadic Successors. This time we give a direct algorithm for model checking and detailed …time upper bound where a number of different parameters are taken into count (i.e. a number of agents, a number of states, knowledge depth, formula size). We present a toy experiment with this algorithm that encourages our hope that the algorithm can be used in practice. Show more

Citation: Fundamenta Informaticae, vol. 72, no. 1-3, pp. 347-361, 2006

Authors: Skowron, Andrzej | Stepaniuk, Jarosław | Peters, James | Swiniarski, Roman

Article Type: Research Article

Abstract: This paper considers the problem of how to establish calculi of approximation spaces. Approximation spaces considered in the context of rough sets were introduced by Zdzisław Pawlak more than two decades ago. In general, a calculus of approximation spaces is a system for combining, describing, measuring, reasoning about, and performing operations on approximation spaces. An approach to achieving a calculus of approximation spaces that provides a basis for approximating reasoning in distributed systems …of cooperating agents is considered in this paper. Examples of basic concepts are given throughout this paper to illustrate how approximation spaces can be beneficially used in many settings, in particular for complex concept approximation. The contribution of this paper is the presentation of a framework for calculi of approximation spaces useful for approximate reasoning by cooperating agents. Show more

Keywords: rough sets, approximation spaces, concept approximation, learning, approximate reasoning

Citation: Fundamenta Informaticae, vol. 72, no. 1-3, pp. 363-378, 2006

Authors: Stefanowski, Jerzy | Wilk, Szymon

Article Type: Research Article

Abstract: The paper addresses problems of improving performance of rule-based classifiers constructed from imbalanced data sets, i.e., data sets where the minority class of primary importance is under-represented in comparison to majority classes. We introduced two techniques to detect and process inconsistent examples from the majority classes in the boundary between the minority and majority classes. Both these techniques differ in the way of processing inconsistent boundary examples from the majority classes. The first …approach removes them, while the other relabels them as belonging to the minority class. The experiments showed that the best results were obtained for the filtering technique, where inconsistent majority class examples were reassigned to the minority class, combined with a classifier composed of decision rules generated by the MODLEM algorithm. Show more

Keywords: Knowledge Discovery, Data Mining, Rough Sets, Classification, Class Imbalance, Rule Induction

Citation: Fundamenta Informaticae, vol. 72, no. 1-3, pp. 379-391, 2006

Authors: Suraj, Zbigniew | Gayar, Neamat El | Delimata, Pawel

Article Type: Research Article

Abstract: During the past decade methods of multiple classifier systems have been developed as a practical and effective solution for a variety of challenging applications. A wide number of techniques and methodologies for combining classifiers have been proposed in the past years in literature. In our work we present a new approach to multiple classifier systems using rough sets to construct classifier ensembles. Rough set methods provide us with various useful techniques of data classification. …In the paper, we also present a method of reduction of the data set with the use of multiple classifiers. Reduction of the data set is performed on attributes and allows to decrease the number of conditional attributes in the decision table. Our method helps to decrease the number of conditional attributes of the data with a small loss on classification accuracy. Show more

Keywords: multiple classifier systems, k-NN, reduction, feature selection

Citation: Fundamenta Informaticae, vol. 72, no. 1-3, pp. 393-406, 2006

Authors: Winkowski, Józef

Article Type: Research Article

Abstract: The paper is concerned with algebras which can be obtained by endowing sets of processes of Petri nets with a sequential and a parallel composition. The considered algebras are categories with additional structures and special properties. It is shown that all structures which enjoy such properties can be represented as algebras of processes of Petri nets.

Keywords: Petri nets, states, processes, sequential composition, parallel composition, category, partial monoid

Citation: Fundamenta Informaticae, vol. 72, no. 1-3, pp. 407-420, 2006

Authors: Wolski, Marcin

Article Type: Research Article

Abstract: The present article deals with the problem whether and how the bilattice orderings of knowledge ⩽_k and truth ⩽_t might enrich the theory of rough sets. Passing to the chief idea of the paper, we develop a bilattice-theoretic generalisation of the concept of rough set to be called A-approximation. It is proved that A-approximations (induced by a topological approximation space) together with the knowledge ordering ⩽_k constitute a complete partial …order (CPO) and that the meet and join operations induced by the truth ordering ⩽_t are continuous functions with respect to ⩽_k . Crisp sets are then obtained as maximal elements of this CPO. The second part of this article deals with the categorical and algebraic properties of A-approximations induced by an Alexandroff topological space. We build a *-autonomous category of A-approximations by means of the Chu construction applied to the Heyting algebra of open sets of Alexandroff topological space. From the algebraic point of view A-approximations under ⩽_t ordering constitute a special Nelson lattice and, as a result, provide a semantics for constructive logic with strong negation. Such lattice may be obtained by means of the twist construction over a Heyting algebra which resembles very much the Chu construction. Thus A-approximations may be retrived from very elementary structures in elegant and intuitive ways. Show more

Keywords: rough set, approximation, bilattice, complete partial order, *-autonomous category, Chu construction, Nelson lattice

Citation: Fundamenta Informaticae, vol. 72, no. 1-3, pp. 421-435, 2006