Fundamenta Informaticae - Volume 74, issue 2-3

Authors: Bednarczyk, Marek A.

Article Type: Research Article

Abstract: It has been observed that various synchronisation operators underlying the modular design of concurrent systems can be explained as pullbacks in suitable categories of concurrent systems. Here, the boundaries of such approach are investigated. For this purpose we study the issue of completeness in categories of trace monoids. It turns out that (finite) completeness is achieved if trace monoids with concurrency preserving homomorphisms are considered. Taking arbitrary monoid homomorphisms leads, in general, …to incompleteness. The results obtained are used to reveal an area in which the code problem for trace monoids, undecidable in general, has always a positive answer. Show more

Keywords: Theory of computation, software/hardware design and implementation, concurrency, partially commutative free monoids, Mazurkiewicz traces, code problem

Citation: Fundamenta Informaticae, vol. 74, no. 2-3, pp. 167-187, 2006

Authors: Chang, Chin-Chen | Lin, Chih-Yang

Article Type: Research Article

Abstract: Reversible steganography allows an original image that has gone through the embedding process to be completely restored after the extraction of the embedded data. In this paper, we propose a reversible scheme with a high embedding capacity for VQ compressed images. Our reversible method is based on a prediction strategy and takes advantage of the local characteristics of the image. Since the location map is usually a necessary part of a reversible scheme, two methods, shifting …and relocating, are also proposed to reduce the size of the location map. As the experimental results show later, our method outperforms previous schemes in terms of embedding capacity and image quality. To be more specific, with low distortion, the embedding capacity of the proposed methods can be higher than one bit per index value. Show more

Keywords: Reversible data embedding, prediction, steganography

Citation: Fundamenta Informaticae, vol. 74, no. 2-3, pp. 189-207, 2006

Authors: Dimov, Georgi | Vakarelov, Dimiter

Article Type: Research Article

Abstract: This work is in the field of region-based (or Whitehedian) theory of space, which is an important subfield of Qualitative Spatial Reasoning (QSR). The paper can be considered also as an application of abstract algebra and topology to some problems arising and motivated in Theoretical Computer Science and QSR. Different axiomatizations for region-based (or Whiteheadian) theory of space are given. The most general one is introduced under the name "Contact Algebra" Adding some extra …first- or secondorder axioms to those of contact algebras, some new or already known algebraic notions are obtained. Representation theorems and completion theorems for all such algebras are proved. Extension theories of the classes of all semiregular T_0 -spaces and all N-regular (a notion introduced here) T_1 -spaces are developed. Show more

Keywords: Qualitative Spatial Reasoning, mereological relations, contact relations, contact algebras, region-based theories of space, RCC models, representation theorems, extensions, completion

Citation: Fundamenta Informaticae, vol. 74, no. 2-3, pp. 209-249, 2006

Authors: Dimov, Georgi | Vakarelov, Dimiter

Article Type: Research Article

Abstract: This paper is the second part of the paper [2]. Both of themare in the field of region-based (or Whitehedian) theory of space, which is an important subfield of Qualitative Spatial Reasoning (QSR). The paper can be considered also as an application of abstract algebra and topology to some problems arising and motivated in Theoretical Computer Science and QSR. In [2], different axiomatizations for region-based theory of space were given. The most general one was introduced …under the name "Contact Algebra". In this paper some categories defined in the language of contact algebras are introduced. It is shown that they are equivalent to the category of all semiregular T_0 -spaces and their continuous maps and to its full subcategories having as objects all regular (respectively, completely regular; compact; locally compact) Hausdorff spaces. An algorithm for a direct construction of all, up to homeomorphism, finite semiregular T_0 -spaces of rank n is found. An example of an RCC model which has no regular Hausdorff representation space is presented. The main method of investigation in both parts is a lattice-theoretic generalization of methods and constructions from the theory of proximity spaces. Proximity models for various kinds of contact algebras are given here. In this way, the paper can be regarded as a full realization of the proximity approach to the region-based theory of space. Show more

Keywords: Qualitative Spatial Reasoning, mereological relations, contact relations, contact algebras, region-based theories of space, RCC models, equivalent categories, semiregular T_i-spaces (i=0,1,2), weakly regular spaces, N-regular spaces, regular spaces, OCE-regular spaces, finite semiregular T_0-spaces, compact (locally compact, completely regular) Hausdorff spaces, proximity spaces, proximity models

Citation: Fundamenta Informaticae, vol. 74, no. 2-3, pp. 251-282, 2006

Authors: Düntsch, Ivo | Winter, Michael

Article Type: Research Article

Abstract: Rough relation algebras arise from Pawlak's information systems by considering as object ordered pairs on a fixed set X. Thus, the subsets to be approximated are binary relations over X, and hence, we have at our disposal not only the set theoretic operations, but also the relational operators; ˘, and the identity relation 1'. In the present paper, which is a continuation of [6], we further investigate the structure of abstract rough relation algebras.

Keywords: Rough sets, Stone algebras, relation algebras

Citation: Fundamenta Informaticae, vol. 74, no. 2-3, pp. 283-300, 2006

Authors: Hitzler, Pascal | Krötzsch, Markus | Zhang, Guo-Qiang

Article Type: Research Article

Abstract: Formal concept analysis has grown from a new branch of the mathematical field of lattice theory to a widely recognized tool in Computer Science and elsewhere. In order to fully benefit from this theory, we believe that it can be enriched with notions such as approximation by computation or representability. The latter are commonly studied in denotational semantics and domain theory and captured most prominently by the notion of algebraicity, e.g. of lattices. In this paper, …we explore the notion of algebraicity in formal concept analysis from a category-theoretical perspective. To this end, we build on the notion of approximable concept with a suitable category and show that the latter is equivalent to the category of algebraic lattices. At the same time, the paper provides a relatively comprehensive account of the representation theory of algebraic lattices in the framework of Stone duality, relating well-known structures such as Scott information systems with further formalisms from logic, topology, domains and lattice theory. Show more

Keywords: Algebraic lattice, Formal concept analysis, Domain theory, Stone duality, Category theory

Citation: Fundamenta Informaticae, vol. 74, no. 2-3, pp. 301-328, 2006

Authors: Kalyanasundaram, Bala | Velauthapillai, Mahe

Article Type: Research Article

Abstract: When learning a concept the learner produces conjectures about the concept he learns. Typically the learner contemplates, performs some experiments, make observations, does some computation, thinks carefully (that is not output a new conjecture for a while) and then makes a conjecture about the (unknown) concept. Any new conjecture of an intelligent learner should be valid for at least some "reasonable amount of time" before some evidence is found that the conjecture is false. Then maybe …the learner can further study and explore the concept more and produce a new conjecture that again will be valid for some "reasonable amount of time". In this paper we formalize the idea of reasonable amount of time. The learners who obey the above constraint are called "Thoughtful learners" (TEX learners). We show that there are classes that can be learned using the above model. We also compare this leaning paradigm to other existing ones. The surprising result is that there is no capability intervals in team TEX-type learning. On the other hand, capability intervals exist in all other models. Also these learners are orthogonal to the learners that have been studied in the literature. Show more

Keywords: Inductive Inference, mind changes, errors, thoughtful machines

Citation: Fundamenta Informaticae, vol. 74, no. 2-3, pp. 329-340, 2006

Authors: Nadarajah, Saralees | Kotz, Samuel

Article Type: Research Article

Abstract: The exact distribution of the linear combination αX + βY is derived when X and Y are independent logistic and Gumbel random variables. A measure of entropy of the linear combination is investigated. Computer programs are provided for generating tabulations of the percentage points associated with the linear combination. The work is motivated by problems in automation, control, fuzzy sets, neurocomputing and other areas of computer science.

Keywords: Entropy, Gumbel distribution, Linear combinations of random variables, Logistic distribution

Citation: Fundamenta Informaticae, vol. 74, no. 2-3, pp. 341-350, 2006

Authors: Shah, Mohak | Sokolova, Marina | Szpakowicz, Stan

Article Type: Research Article

Abstract: We introduce Process-Specific Feature Selection, an innovative procedure of feature selection for textual data. The procedure applies to data gathered in person-to-person communication. The procedure relies on the knowledge of the processes that govern such communication. It is general enough to represent data in a wide variety of domains. We present a case study of electronic negotiation, in which participants exchange text messages. We present the empirical results of classifying the outcomes of electronic …negotiations based on such texts. The results achieved using process-specific feature selection are marginally better than those afforded by several traditional feature selection methods. We show that this tendency is consistent across several learning paradigms. Show more

Keywords: textual data, feature selection, electronic negotiations, machine learning

Citation: Fundamenta Informaticae, vol. 74, no. 2-3, pp. 351-373, 2006

Authors: Szpyrka, Marcin

Article Type: Research Article

Abstract: RTCP-nets are a subclass of timed coloured Petri nets defined for modelling and analysis of embedded real-time systems. One of the main advantages of strongly bounded RTCP-nets is a possibility to present the set of reachable states of an RTCP-net using a finite reachability and/or coverability graph. These graphs can be used to verify most of the net's properties, including the timing ones. The paper discusses analysis methods based on these graphs. A formal definition of …RTCP-nets and a survey of their properties are also presented in the paper. Show more

Keywords: RTCP-nets, analysis, reachability graphs, coverability graphs

Citation: Fundamenta Informaticae, vol. 74, no. 2-3, pp. 375-390, 2006