Abstracts:

Anestis A. Toptsis
Dept. of Computer Science and Mathematics, York University, Atkinson College, Toronto, Ontario, M3J 1P3, Canada; anestis@yorku.ca

Integration of data and knowledge bases presents a major challenge of efficient processing linear recursive queries on a very large data volumes. A notalbe example is the computation of the transitive closure. Although a plethora of sequential transitive closure algorithms have been developed, parallel transitive closure algorithms are rather scarce. In this paper we present, analyze, and compare six parallel algorithms for the computation of the transitive closure of a database relation. Three of the algorithms compute the complete closure, while the other three are modifications tailored for the computation of the restricted closure. The algorithms make no assumptions about data organization and do not require any present indices or pre processed data. A share-nothing parallel architecture is assumed for all algorithms. The analysis and performance evaluation shows that the restricted closure algorithms outperform the complete closure ones bya significant factor. Moreover, four of the six presented algorithms possess load balancing and scalability properties that make them far superior to the conventional transitive closure parallel methods.(pp. 7-25)

Keywords: Transitive closure, parallel processing, relational database, losd balancing, load

Alenka Znidarsic
Jozef Stefan Institute, Department of Computer Automation and Control, Jamova39, 61111 Ljubljana, Slovenia; alenka.znidarsic@ijs.si
Victor J. Terpstra , Henk B. Verbruggen
Delft University of Technology, Department of Electrical Engineering, Control Laboratory, P. O. Box 5031, 2600 GA Delft, The Netherlands

Detection and diagnosis of faults (FDD) in technical systems represent an important segment of intelligent and fault-tolerant systems. In the article we present the qualitative FDD approach proposed by Larsson and based on Multilevel Flow Modeling representation process. The contribution of this article regards evaluation of this method on a simulated water-level process controlled by feedback. The MFM diagnostic expert system, together with the continuous simulation of the process, is implemented in a real-time expert system tool G2. Based on results perspectives for further work will also be given.(pp. 27-36)

Keywords: Multistrategy learning, advice taking, compilation, operationalization, genetic algorithms

A. Mahmood
Department of Electrical Engineering, King's College London, The Strand, London WC2R 2LS, U.K; a.mahood@bay.cc.kcl.ac.uk
H. U. Khan
Department of Electrical Engineering, King's College London, The Strand, London WC2R 2LS, U. K.
H. A. Fatmi
Department of Electrical Engineering, King'sCollege London, The Strand, London WC2R 2LS, U. K.

The problem of adaptive data allocation is distributed information systems to minimize the overall communication and storage costs is discussed. A key problem of economical estimation of future file utilization pattern is described and an algorithm based on the Gabor-Kolmogorov learning process is presented to estimate the future access and the update patterns. An adaptive algorithm to reallocate data in a computer network is proposed. The reallocation algorithm chooses the optimal allocation using two objective functions and the best fit strategy. also, a distributed candidate selection algorithm is presented to reduce the number of files and nodes in the reallocation process. The simulation results are presented to demonstrate the accuracy and the efficiency of the proposed algorithms.(pp. 37-46)

Keywords: File allocation, distributed data management, computer networks, heuristics

M. Ostroversnik
Jozef Stefan Institute, Jamova 39, 61 000 Ljubljana, Slovenia
Z. Sehic , B. Zupancic
Faculty of Electrical and Computer Engineering, 61 000 Ljubljana, Trzaska 25, Slovenia
M. Sega
Metronik d. o. o., Stegne 21, 61 000 Ljubljana, Slovenia

The work deals with the representation of the concepts of program package PIDMaster for on-site signal analysis, system modeling and controller's synthesis. A user-friendly interface is introduced which enables comfortable work also for less experienced users. The required user-friendliness has been achieved by the use of window interface management system. Central points of the new interface are the so-called movable graphical objects. Their usage in the phase of system parameter estimation is explained thoroughly.(pp. 47-53)

Keywords: OOP, Software Engineering, Control System Design, PID Control

C. Wohlin
Department of Communication Systems, Lund Institute of Technology, Lund University, Box 118, S-221 00 Lund, Sweden

This article presents an evaluation method of software quality attribute during software design with a high-level design technique. The attributes considered are real time functional behavior, performance (in terms of capacity) and reliability. The method is based on transformation of the software design documents and simulation models of hardware architecture in terms of usage of the system. The method provides an opportunity to concentrate on software, architecture and usage of the system one by one and facilitates analysis of the software system long before it is taken into operation, which is particularly valuable for safety-critical software and other complex software systems. This implies that important information concerning both functionality, performance and reliability can be studied early in the development, so that re-design can be performed instead of implementing a poor solution. These insights become more and more.(pp. 55-70)

Keywords: quality evaluation, performance, functional analysis, software reliability, simulation, software metrics, Cleanroom

Jurij Silc
Jozef Stefan Institute, Laboratory for Computer Architectures, Jamova 39, Ljubljana, Slovenia; jurij.silc@ijs.si

The paper describes objectives of high-level synthesis. It concentrates on operation scheduling strategies and the interaction with the resource allocation. Some transformational and iterative/constructive scheduling algorithms are described. Moreover, a new scheduling/allocation approach is presented and compared with other known algorithms. Finally, some open problems of the high-level synthesis are given.(pp. 71-79)

Keywords:High-level synthesis, scheduling, allocation

Bojan Nemec
Jozef Stefan Institute, University of Ljubljana, Ljubljana, Jamova 39, Slovenia; bojan.nemec@ijs.si
Leo Zlajpah
Jozef Stefan Institute, University of Ljubljana, Ljubljana, Jamova 39, Slovenia

The paper describes the implementation of the adaptive force control of an industrial robot. The implemented algorithm is a position based hybrid control scheme with adaptation to the environment stiffness. Control scheme is sensitive to the changes in environment stiffness. We solved this problem by the adaptive controller. Implementation problems on the robot controller are also discussed. The proposed control method is easy to implement and can be applied to existing industrial robots fitted with a conventional position controller. The performance of the force controlled manipulator with the proposed control law was tested with the computer simulation and by using the real robot.(pp. 81-91)

Keywords: Force control, robot control, adaptive control

Hiroshi Suematsu
Japan Electronic Dictionary Research Institute, Ltd. (EDR), Mita-Kokusai Bldg. Annex, 4-28, Mita 1-chome, Minato-ku, Tokyo, Japan; suematsu@edr.co.jp

The current status of the EDR electronic dictionary project and its future plan is reported in this paper. The electronic dictionary is not a mere electronic version of a book-form dictionary (i.e. machine-readable dictionary, MRD). It is a dictionary for computer processing of natural languages, e. g. machine translation. It captures lexical information, such as lemmas, parts of speech, and word senses, in a machine-tractable way, to support various natural language processing (NLP) approaches on the level of morphology, syntax, semantics, and pragmatics. A considerable vocabulary size needs to be covered in a consistent way, and implicit information left to the human reader in the case of a book-form dictionary, has to be explicitly stated in a computer-processable manner. In constructing such a large-scale electronic dictionary, a very large-scale corpus is need to extract linguistic information, and to verify data described in the electronic dictionary. The corpus is gaining more importance along with the recent avocation of example-based machine translation. The EDR electronic dictionary project is one of the earliest efforts of this kind, and has one more year before it ends. EDR is now in the process of compiling and producing the final result of 8 years' work. The EDR Electronic Dictionary, or for short, EDR dictionary, has reached a level competent enough to be used for R&D, provision of it has started as the beta test. There is concern, however, about the slow progress in the English section of the Dictionary. Various views and opinions are currently under discussion on the future plan for the EDR Electronic Dictionary.(pp. 93-96)

Keywords: beta test, bilingual dictionary concept dictionary, cooccurrence dictionary, current status, EDR, EDR corpus, electronic dictionary, project, structure, text base, word dictionary