Lecture Notes in Computer Science. Edited by G. Goos and J. Hartmanis Advisory Board: W. Brauer D. Gries J. Stoer

Transcription

1 Lecture Notes in Computer Science 502 Edited by G. Goos and J. Hartmanis Advisory Board: W. Brauer D. Gries J. Stoer g

2 J. Bfirzdin.g D. BjCrner (Eds.) Baltic Computer Science Selected Papers Springer-Verlag Berlin Heidelberg NewYork London Paris Tokyo Hong Kong Barcelona Budapest

3 Series Editors Gerhard Goos GMD Forschungsstelle Universit~it Karlsruhe Vincenz-Priessnitz-Strage 1 W-7500 Karlsruhe, FRG Juris Hartmanis Department of Computer Science Cornell University Upson Hall Ithaca, NY 14853, USA Volume Editors Janis B~rzdin. g Institute of Mathematics and Computer Science University of Latvia Boulevard Rainis 29, Riga , Latvia Dines BjCrner Department of Computer Science, Building 344 Technical University of Denmark DK-2800 Lyngby, Denmark CR Subject Classification (1991): D.1-3, El-3 ISBN Springer-Verlag Berlin Heidelberg New York ISBN Springer-Verlag New York Berlin Heidelberg This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broadcasting, reproduction on microfilms or in other ways, and storage in data banks. Duplication of this publication or parts thereof is only permitted under the provisions of the German Copyright Law of September 9, 1965, in its current version, and a copyright fee must always be paid. Violations fall under the prosecution act of the German Copyright Springcr-Verlag Berlin Heidelberg 1991 Printed in Germany Printing and binding: Druckhaus Beltz, Hemsbach/Bergstr. 2145/ Printed on acid-free paper

4 P refa ce There is no 'Soviet Computer Science'. There are Estonian, Latvian, and Lithuanian cultures, as there are Armenian, Russian, Ukrainian, and many other cultures within the USSR. The cultures of the Baltics have bound together by centuries of history, some of it not so enlightening. The Baltics computer science culture is amply demonstrated in this volmune. It has for too long not been widely accessible in the English literature. It is a refreshing reminder of man's ability to contribute despite troublesome times. The usual benefits of free, international scientific co-operation, as most readers of this volume experiences it, of unhindered access to literature, of speedy exchange of results in the form, for example, of broad, international conference participation, was not a basic instrument of our colleagues in the east. Science is international, and the more local science fits in with international developments, the more it obviously demonstrates its internationality. The present volume reflects work that is both internationally as well as locally inspired. It should surprise me if the present volume could not - now - inspire research on a broader, international scale, as it has inspired other researchers in the USSR. Attempts to formulate computer science results in the USSR in the classical framework of mathematics, but cast in the dialectical constructs of so-called cybernetics seems to have failed. Luckily the Baltics scientists did not fall into that trap. With a strong background - also in Russian mathematical logic - we see in this volume refreshing contributions, which, in addition, seem to fit better into the computer science tradition generally propagated. Things are changing, however. We have seen, in the span of a few years, several productive, international conferences in the USSR 1. This volume did not grow 1See for example: COLOG'88, Springer Lecture Notes in Computer Science, Vol. 417, and Logic at Bofik'89, Springer Lecture Notes in Computer Science, Vo]. 363.

5 VI out of such a conference, however, although it seems to me that its publication could set a precedence for other groupings of scientists across the combine of Russia, Ukraine, etc., to demonstrate their insight and results. I am sure that, in future, we shall see the Baltic Republics form a vital link between the science of Russia - et cetera - on one hand, and the rest of the world, on the other hand. The foreword by the main editor, Jan B~rzdi.n~, gives, as could be expected, a clear overview of this volume and its contributions. I shall therefore only here express the joy and pleasure I feel in having been able to bring this volume out. Technical University of Denmark

6 VII Foreword This volume offers a significant insight into Baltic computer science within the scope of the last years. The volume contains both the results published mainly in Russian and completely new results. Four research directions can be distinguished in Baltic computer science. They are represented in four parts of the volume: Deductive synthesis of programs (Estonia), Inductive synthesis of programs (Latvia), Automatic test case generation (Latvia), Specification and verification of distributed systems (Lithuania). Several other research activities are included in the fifth part: Miscellaneous. Deductive synthesis of programs. In the 1980s at the Institute of Cybernetics, Tallinn, an advanced knowledge-based programming system PRIZ was developed by E. Tyugu and his research group. The system PRIZ combines conventional programming technique with automatic synthesis of programs from problem specifications. The paper by G. Mints and E. Tyugu contains a general description and logical basis of the system PRIZ. A new approach to the semantics of specification languages based on structural synthesis ideas is proposed in the paper by G. Mints, J. Smith and E. Tyugu. A knowledge-based approach to the semantics of problem-oriented languages is considered in the paper by M. Meriste, J. Penjam. T. Tammet's paper is devoted to automatic theorem proving. Inductive synthesis ofprograrns. In the 1970s and early 1980s the problem of inductive synthesis was investigated mainly on a recursive-theoretic level. Major results concerning this approach are presented in the papers by R. Freivalds and by R. Freivalds, J. B~rzdin~ and J. Podnieks. In the 1980s new models of inductive synthesis based on detection of purely syntactical analogies were developed by a research group at the University of Latvia. The papers by A. Br~zma and E. Kinber are devoted to these models. A new approach to the problem of inductive synthesis based on TRS is presented in the paper by G. B~rzdi.n~. Autorna~ic f, est case generation. The theoretical basis of automatic test generation is developed in the paper by A. Auzin~,, J. B~rzdin~, J. Bi evskis, K. Cer~ns, and A. Kalni.n~i.

7 VIII it is proved that for a wide class of programs the problem of automatic construction of complete test sets according to criterion (71 is algorithmically solvable. The paper by J. Borzovs, A. Kalnin.] and I. Medvedis is devoted to practical methods of automatic test generation for distributed real time systems. Specit~cation and verit~cation of distributed systems. In H. Pranevitchius' paper new methods and tools for specification and verification of computer network protocols are proposed. In K. Ge as' paper the axiomatic approach for formalization of distributed systems is discussed. The completeness problems of temporal logic are considered in R. Pliu~,kevi ius'paper. Miscellaneous. The paper by M. Auguston describes a powerful compiler writing system successfully used in many projects. The paper by R. Freivaids contains several important results showing the advantages of probabilistic automata over deterministic ones. In conclusion it should be pointed out that many activities in the field of computers in the Baltic states are not featured in the volume. First, those related to computer networks, digital exchange systems, artificial intelligence are not reported. Also, finite automata research carried out in the late 1960s and early 1970s is not reflected in this volume. Nonetheless we hope the volume to be of interest for the people working in computer science. Riga April 1991 J~nis B~rzdi.n~ Dedication This volume is dedicated to Professor Boris Avramovich Trakhtenbrot Father of Baltic Computer Science on the occasion of his 70th birthday in June 1991

8 Contents Deductive Synthesis of Programs The Programming System PRIZ... 1 Ca. Mints, E. Tyugu (Tallinn) Type-theoretical Semantics of Some Declarative Languages G. Mints, J.M. Smith, E. Tyugu (Tallinn, G6teborg) Using Resolution for Deciding Solvable Classes and Building Finite Models T. Tammet (Tallinn) Toward Knowledge-based Specifications of Languages M. Meriste (Tartu), J. Penjam (Tallinn) Inductive Synthesis of Programs Inductive Inference of Recursive Functions: Qualitative Theory R. Freivalds (Riga) Inductive Inference of Recursive Functions: Complexity Bounds R. Freivalds, J. B~rzdinll, K. Podnieks (Riga) Inductive Synthesis of Dot Expressions A. Br~zma (Riga) Some Models of Inductive Syntactical Synthesis from Sample Computations E. Kinber (Riga) Inductive Synthesis of Term Rewriting Systems G. B~rzdi.n~ (Riga) Automatic Test Case Generation Automatic Construction of Test Sets: Theoretical Approach A. huzin~,, J. B~rzdi.n~, J. Bi~evskis, K. (~er,~ns, A. Kalni.n~ (Riga)

9 Automatic Construction of Test Sets: Practical Approach J. Borzovs, A. Kalning, I. Medvedis (Riga) Specification and Verification of Distributed Systems Aggregate Approach for Specification, Validation, Simulation and Implementation of Computer Network Protocols H. Pranevitchius (Kaunas) A Compositional Proof System for Distributed Programs K. Ge~as (Vilnius) Investigation of Finitary Calculus for a Discrete Linear Time Logic by means of Infinitary Calculus R. Pliu~,kevi~.ius (Vilnius) Miscellaneous RIGAL - a Programming Language for Compiler Writing M. Auguston (Riga) Complexity of Probabilistic Versus Deterministic Automata R. Freivalds (Riga) About the Authors