Journal:Informatica
Volume 19, Issue 3 (2008), pp. 447–460
Abstract
Multidimensional scaling is a technique for exploratory analysis of multidimensional data widely usable in different applications. By means of this technique the image points in a low-dimensional embedding space can be found whose inter-point distances fit the given dissimilarities between the considered objects. In this paper dependence of relative visualization error on the dimensionality of embedding space is investigated. Both artificial and practical data sets have been used. The images in three-dimensional embedding space normally show the structural properties of sets of considered objects with acceptable accuracy, and widening of applications of stereo screens makes three-dimensional visualization very attractive.
Journal:Informatica
Volume 19, Issue 3 (2008), pp. 421–446
Abstract
It is well known that a formal framework for the schema matching problem (SMP) is important because it facilitates the building of algorithm model and the evaluation of algorithms. An algebraic framework for schema matching is developed in this paper. First, based on universal algebra, we propose a meta-meta structure for schema, which is named multi-labeled schema. This definition has a distinctive feature: it is able to formally describe any particular style of schemas, and transforms a schema and other available information into a finite structure over specific signature. Later, we introduce a formal definition of schema matching that is called multivalent matching. Then, we formulize SMP as a schema homomorphism problem, and prove that SMP is equivalent to finding a semantic homomorphism from one schema to another. These results lead to the main contribution of this paper: an algebraic framework for SMP. This framework builds the algorithm model for SMP. Thirdly, we show a classification of schema matching based on the algebraic framework. Finally, we discuss the relations between matching cardinality and subclasses of schema homomorphism.
Journal:Informatica
Volume 19, Issue 3 (2008), pp. 403–420
Abstract
New information technologies provide a possibility of collecting a large amount of fundus images into databases. It allows us to use automated processing and classification of images for clinical decisions. Automated localization and parameterization of the optic nerve disc is particularly important in making a diagnosis of glaucoma, because the main symptoms in these cases are relations between the optic nerve and cupping parameters. This article describes the automated algorithm for the optic nerve disc localization and parameterization by an ellipse within colour retinal images. The testing results are discussed as well.
Journal:Informatica
Volume 19, Issue 3 (2008), pp. 391–402
Abstract
Non-invasive physiological monitors are important subsystems of intensive care informatic systems. New innovative information methods and technology are presented for non-invasive human brain volumetric pulse wave physiological monitoring.
Experimental study of a new, non-invasive ultrasonic intracranial pulse wave monitoring technology show the reactions of non-invasively recorded intracranial blood volume pulse waves (IBVPW) on healthy volunteers in different human body positions. A group of 13 healthy volunteers was studied.
Body posture caused IBVPW, subwaves changes, ΔP2 = 18% and ΔP3 = 11%. The value of the IBVPW amplitude's ratio in supine and upright positions was 1.55 ± 0.61.
Journal:Informatica
Volume 19, Issue 3 (2008), pp. 377–390
Abstract
We investigate applicability of quantitative methods to discover the most fundamental structural properties of the most reliable political data in Lithuania. Namely, we analyze voting data of the Lithuanian Parliament. Two most widely used techniques of structural data analysis (clustering and multidimensional scaling) are compared. We draw some technical conclusions which can serve as recommendations in more purposeful application of these methods.
Journal:Informatica
Volume 19, Issue 3 (2008), pp. 363–376
Abstract
This paper is concerned with the problem of image analysis based detection of local defects embedded in particleboard surfaces. Though simple, but efficient technique developed is based on the analysis of the discrete probability distribution of the image intensity values and the 2D discrete Walsh transform. Robust global features characterizing a surface texture are extracted and then analyzed by a pattern classifier. The classifier not only assigns the pattern into the quality or detective class, but also provides the certainty value attributed to the decision. A 100% correct classification accuracy was obtained when testing the technique proposed on a set of 200 images.
Journal:Informatica
Volume 19, Issue 3 (2008), pp. 345–362
Abstract
In this paper, we present a method for describing the syntax and semantics of viewcharts. Viewcharts is a visual formalism for describing the dynamic behavior of system components. We define the syntax of viewcharts as attributed graphs and, based on this graph, describe dynamic semantics of viewcharts by object mapping automata. This approach covers many important constructs of viewcharts, including hierarchy of views, ownership of elements, scope, and composition of views in SEPARATE, OR and AND ways. It also covers completion and interlevel transitions as well as history transitions without violating the independence of views. Viewcharts was originally based on statecharts; in this paper we also change the basis of viewcharts to an extended version of Finite State Machine (EFSM).
Journal:Informatica
Volume 19, Issue 3 (2008), pp. 321–344
Abstract
The purpose of the research described in this paper is to propose a framework and supporting tools that will help software companies to establish formalised methods that will be technically and socially sound with their needs. Following the framework the companies can asses and improve their existing ways of working, capture them into formalised methods and continuously enrich them based on the past development experiences. Furthermore, the formalised methods that are designed based on the suggested framework are flexible and can be automatically adjusted by the supporting tools to suite circumstances of a particular project or team. This paper describes the framework philosophy and its tool support.
Journal:Informatica
Volume 19, Issue 2 (2008), pp. 303–314
Abstract
Multi-criteria decision making is used in many areas of human activities. Each alternative in multi-criteria decision making problem can be described by a set of criteria. Criteria can be qualitative and quantitative. They usually have different units of measurement and different optimization direction. The normalization aims at obtaining comparable scales of criteria values. The normalization of criteria values is not always needed, but it may be essential. In the new program LEVI 3.1 the following normalization methods are possible: vector, linear scale, non-linear and new logarithmic techniques. Logarithmic normalization has never been used before. The present research is focused on introducing a new logarithmic method for decision making matrix normalization.
Journal:Informatica
Volume 19, Issue 2 (2008), pp. 285–302
Abstract
With rapid growth of mobile wireless networks, handheld devices are popularly used by people and many mobile applications have been rapidly developed. Considering the limited computing capability of smart cards or mobile devices, the security scheme design suitable for these mobile devices is a nontrivial challenge. A user authentication scheme is a mechanism to authenticate a remote user over an open network. In 2006, Das et al. proposed an identity (ID)-based remote user authentication scheme with smart cards using bilinear pairings. Unfortunately, their scheme is insecure against forgery attack. Recently, Giri and Srivastava proposed an improved scheme to overcome the forgery attack. The computational cost required by the Giri–Srivastava scheme is expensive, especially for smart cards with limited computing capability. In addition, the Giri–Srivastava scheme is unable to be used for a multi-server environment. This paper presents an efficient and secure ID-based remote user authentication scheme using bilinear pairings. Based on the computational Diffie–Hellman assumption, we show that the proposed scheme is secure against existential forgery on adaptively chosen-message and ID attack in the random oracle model. As compared with the recently proposed pairing-based authentication schemes, our scheme has better performance in term of the computational cost and it is suitable for a multi-server environment in distributed networks. Performance analysis and experimental data of related pairing operations on smartcards are given to demonstrate that our scheme is well suited for mobile devices with limited computing capability.