Specification and Development of Interactive Systems: Focus on Streams, Interfaces, and Refinement

356 Pages·2001·7.426 MB·English

by  Manfred Broy, Ketil Stølen

Monographs in Computer Science
Editors
David Gries
Fred B. Schneider
Springer Science+Business Media, LLC
Monographs in Computer Science
Abadi and Cardelli, A Theory of Objects
Brzozowski and Seger, Asynchronous Circuits
Selig, Geometrical Methods in Robotics
Nielson [editor], ML with Concurrency
Castillo, Gutierrez, and Hadi, Expert Systems and Probabilistic Network Models
Paton [editor], Active Rules in Database Systems
Downey and Fellows, Parameterized Complexity
Leiss, Language Equations
Feijen and van Gasteren, On a Method of Multiprogramming
Broy and St0len, Specification and Development of Interactive Systems: FOCUS on
Streams. Interfaces, and Refinement
Manfred Broy
Ketil St01en
Specification and
Development of
Interactive Systems
Focus on Streams,
Interfaces, and Refinement
With 50 Figures
i
Springer
Manfred Broy Ketil Stf1Jlen
Institut fOr Informatik Sintef Telecom and Informatics
Technische Universităt P.O. Box 124 Blindern
Munchen N-0314 Oslo, Norway
80290 Munchen, Germany [email protected]
[email protected]
and
Department of Informatics
University of Oslo
P.O. Box 1080 Blindern
N-0314 Oslo, Norway
Series Editors:
David Gries Fred B. Schneider
Department of Computer Science Department of Computer Science
The University of Georgia Cornell University
415 Boyd Graduate Studies Research Upson Hali
Center Ithaca, NY 14853-7501, USA
Athens, GA 30602-7404, USA
Library of Congress Cataloging-in-Publication Data
Broy, M., 1949-
Specification and development of interactive systems : Foeus on streams, interfaces,
and refinement / Manfred Broy, Ketil St0len.
p. cm.
Includes bibliographical references and index.
ISBN 978-1-4612-6518-4 ISBN 978-1-4613-0091-5 (eBook)
DOI 10.1007/978-1-4613-0091-5
1. Software engineering. 2. Systems engineering. 1. St0len, Ketil. II. Title.
QA76.758 .B783 2001
003--dc21 00-047090
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© 2001 Springer Seience+Business Media New York
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Preface
This book presents a fundamental mathematical and logical approach to soft
ware and systems engineering. Considering the large number of books de
scribing mathematical approaches to program development, it is important
to explain what we consider to be the specific contribution of our book, to
identify our goals, and to characterize our intended target audience.
Most books dealing with the mathematics and logics of programming and
system development are mainly devoted to programming in the small. This is
in contrast to our book where the emphasis is on modular system development
with the help of component specifications with precisely identified interfaces
and refinement concepts. Our book aims at systems development carried out
in a systematic way, based on a clear mathematical theory.
We do not claim that this book presents a full-blown engineering method.
In fact, this is certainly not a book for the application-driven software engi
neer looking for a practical method for system development in an industrial
context. It is much rather a book for the computer scientist and the scientifi
cally interested engineer who looks for basic principles of system development
and, moreover, its mathematical foundations. It is also a book for method
builders interested in a proper mathematical foundation on which they can
build a practical development method and industrial-strength support tools.
Our principal objective with this book is to show that system develop
ment based on stepwise refinement can be completely carried out within a
mathematical and scientifically respectable theory. We claim that all the en
gineering steps usually found in system developments are supported by our
approach.
In this book we present our method in a rather puristic form. Many prag
matic issues are simply ignored. Nevertheless, we demonstrate the connec
tions and relationships to practical system development; in particular, we
emphasize that there is a bridge from our mathematically well-defined ap
proach to the description techniques used in practice today. It is our goal
to demonstrate that our theory is a scientific basis for many of the prag
matic system description techniques employed in industry. We concentrate
on the scientific basis, however, and do not enter into the more pragmatic
discussions of syntactic sugaring and concrete graphical and textual repre-
vi Preface
sentations. We hope that this book can contribute towards making software
engineering methods cleaner, more systematic, and more reliable in practice.
In our presentation we have tried to keep all the mathematical aspects as
simple as possible. We expect that anyone who knows the most basic elements
of mathematics and predicate logics to be able to read and understand our
book.
Our book addresses both a methodology for system development and
its scientific foundation. We strongly believe that one can only gain a real
understanding of the potential of our approach by trying it out and testing
it on examples. Therefore, at the end of each chapter we provide a number
of exercises. A reader should be able to carry out these exercises after having
read the corresponding chapter carefully.
The work we present in this book is built on top of research carried out
by many scientists within the field of computer science. Our book puts to
gether a variety of their results. In fact, it is based on numerous enlightening
articles written by other computer scientists. Moreover, we owe a lot to our
colleagues at the Technical University in Munich; they have helped us to
develop a better understanding of our method and how it should be pre
sented and explained. We, in particular, gratefully acknowledge the help of
Max Breitling, Frank Dederichs, Max Fuchs, Radu Grosu, IngolfKriiger, Jan
Philipps, Robert Sandner, Bernhard Schatz, Katharina Spies, and Rainer We
ber. 0ystein Haugen visited us on several occasions during a critical stage of
the book work. We thank him for critically reading early drafts and making
many useful suggestions. We also gratefully acknowledge the help of Michael
Streichsbier who during several years patiently implemented our handwritten
notes in Latex.
To all these people we are deeply grateful. We hope the book can be
recognized as an attempt to give back at least some of the understanding we
have gained from them.
November 2000 Manfred Bray
K etil St¢len
Contents
Preface....................................................... v
Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. xiii
1. Introduction.............................................. 1
1.1 Systems............................................... 2
1.2 Specifications.......................................... 3
1.3 Refinement............................................ 6
1.4 Application Domains. . . .. .. . . .. ... . .. . . .. . . . . .. . . .. . . . . . 7
1.5 Development Process and Methodology ................... 8
1.6 Rationale of Focus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.6.1 Classification of Modeling Techniques. . . . . . . . . . . . . . . 9
1.6.2 Description Paradigm. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 10
1. 7 Overview of the Book. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 13
1.7.1 Part 1: Introductory Section. . . . . . . . . . . . . . . . . . . . . .. 13
1. 7.2 Part 2: Mathematical Foundations. . . . . . . . . . . . . . . . .. 14
1. 7.3 Part 3: Specification. . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14
1.7.4 Part 4: Refinement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 14
1.8 How the Book Should Be Read. . . . . . . . . . . . . . . . . . . . . . . . . .. 15
2. A Guided Tour. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19
2.1 Plan for the Tour. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19
2.2 Station 1: Unbounded Buffer. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 21
2.2.1 Streams......................................... 21
2.2.2 Informal Specification. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 22
2.2.3 Task 1.1: A/G Specification.. . .. . . .. .. . . . . .. . . .. . .. 23
2.2.4 Task 1.2: Equational Specification. . . . . . . . . . . . . . . . .. 25
2.2.5 Task 1.3: Equational Specification with Local States.. 28
2.3 Station 2: Unbounded Lossy Buffer. . . . . . . . . . . . . . . . . . . . . .. 29
2.3.1 Task 2.1: Combined Equational and A/G Specification
with Oracles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 30
2.3.2 Task 2.2: Table-Based Specification. . . . . . . . . . . . . . . .. 32
2.4 Station 3: Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 33
2.5 Station 4: Composite Specifications. . . . . . . . . . . . . . . . . . . . . .. 34
viii Contents
2.5.1 Task 4.1: Graphical Specification. . . . . . . . . . . . . . . . . .. 34
2.5.2 Task 4.2: Constraint-Based Specification ............ 34
2.5.3 Task 4.3: Behavioral Refinement ................... 35
2.5.4 Task 4.4: Glass-Box Specification. . . . . . . . . . . . . . . . . .. 36
2.6 Station 5: Time-Sensitive Buffer. . . . . . . . . . . . . . . . . . . . . . . . .. 37
2.6.1 Timed Streams. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 37
2.6.2 Task 5.1: AjG Specification .......... , . . .. . . .. .. . .. 38
2.6.3 Timed versus Untimed Specifications ............... 39
2.6.4 Task 5.2: Conditional Behavioral Refinement. . . . . . . .. 40
2.7 Station 6: Timed Lossy Buffer. . . . . . . . . . . . . . . . . . . . . . . . . . .. 40
2.7.1 Informal Specification. . .. .. . . .. . . . . . . . . . . .. . .. . . .. 41
2.7.2 Task 6.1: AjG Specification ........................ 41
2.7.3 Task 6.2: Conditional Interface Refinement. . . . . . . . .. 42
2.8 Station 7: Timed Driver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 45
2.8.1 Task 7.1: AjG Specification. . .. . . . .. . . .. .. . . .. . .. .. 46
2.8.2 Task 7.2: State Transition Diagram. . . . . . . . . . . . . . . .. 47
2.8.3 Task 7.3: Refinement ............................. 48
2.9 Station 8: Timed Composite Specification ................. 48
2.9.1 Development..................................... 48
3. Basics.................................................... 51
3.1 Sets.................................................. 51
3.2 Tuples................................................ 52
3.3 Functions.............................................. 53
3.4 Types................................................. 53
3.5 Logic................................................. 54
4. Streams.................................................. 57
4.1 Formal Definition of Streams. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 59
4.2 Basic Operators on Streams ............................. 59
4.3 Additional Operators on Streams. . . . . . . . . . . . . . . . . . . . . . . .. 62
4.4 Formal Definition of Timed Streams ...................... 64
4.5 Operators on Timed Streams ............................ 65
5. Specifications............................................. 69
5.1 Classification of Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . .. 70
5.2 Elementary Specifications ............................... 73
5.2.1 Syntax.......................................... 73
5.2.2 Examples ....................................... 74
5.2.3 Semantics....................................... 80
5.2.4 Graphical Representation of Syntactic Interfaces ..... 83
5.3 Composite Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 84
5.3.1 Graphical Style ..................... . . . . . . . . . . . .. 84
5.3.2 Constraint Style. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 85
5.3.3 Operator Style. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 86
Contents ix
5.3.4 Methodological Advice. . . . . . . . . . . . . . . . . . . . . . . . . . .. 87
5.4 Black-Box and Glass-Box Views. . . . . . . . . . . . . . . . . . . . . . . . .. 88
5.5 Parameterized Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 89
5.6 Sheafs and Replications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 91
5.6.1 Sheafs of Channels ............................... 91
5.6.2 Specification Replication. . . . . . . . . . . . . . . . . . . . . . . . .. 93
5.6.3 Dependent Replications . . . . . . . . . . . . . . . . . . . . . . . . . .. 96
6. Examples ................................................. 101
6.1 Alternating Bit Protocol ................................ 101
6.2 Steam Boiler ........................................... 104
6.3 Memory Components ................................... 107
6.3.1 Basic Definitions ................................. 108
6.3.2 Sequential Memory Component .................... 109
6.3.3 Concurrent Memory Component ................... 110
6.3.4 Repetitive Memory Component .................... 111
7. Properties of Specifications ............................... 115
7.1 Safety and Liveness Properties ........................... 115
7.1.1 Formalization of Safety ............................ 116
7.1.2 Formalization of Liveness .......................... 118
7.1.3 Decomposition into Safety and Liveness Parts ........ 119
7.1.4 Safety and Liveness for Specifications ............... 120
7.2 Realizability ........................................... 121
7.2.1 Strategies ....................................... 123
7.2.2 Weak and Strong Realizability ..................... 123
7.2.3 Full Realizability ................................. 126
7.2.4 Preserving Realizability by Composition ............. 128
7.3 Causality for Specifications .............................. 129
7.3.1 Adding Causality to Specifications .................. 129
7.3.2 A Proof Principle Based on Strong Causality ........ 131
7.3.3 Causality and Feedback ........................... 132
8. Equational Specification of State Transitions .............. 137
8.1 I/O Transitions ........................................ 140
8.2 Local States ........................................... 147
8.3 Control States ......................................... 150
8.4 Oracles ................................................ 155
9. Access Control System ................................... 161
9.1 System Architecture .................................... 161
9.2 Functional Properties of the Controllers ................... 165
9.2.1 Central Controller ................................ 165
9.2.2 Local Controller .................................. 165
9.2.3 Panel Controller .................................. 168
x Contents
9.3 Introducing Exception Handling .......................... 170
9.4 Imposing Timing Constraints ............................ 172
9.4.1 Introducing Timeouts ............................. 172
9.4.2 Imposing Constraints On the Response Time ......... 175
10. Tables and Diagrams ..................................... 177
10.1 State Transition Tables .................................. 178
10.2 State Transition Diagrams ............................... 182
10.3 Semantics of State Transition Tables and Diagrams ......... 188
10.3.1 Syntax of State Transition Diagrams ................ 188
10.3.2 Semantics of Deterministic State Transition
Diagrams ....................................... , 189
10.3.3 Semantics of Nondeterministic State
Transition Tables ................................. 191
11. Abracadabra Protocol .................................... 195
11.1 Informal Specification ................................... 195
11.1.1 Protocol Data Units and Parameters ............... , 196
11.1.2 Connection Phase ................................ 197
11.1.3 Data Transfer Phase ............................. , 197
11.1.4 Disconnection Phase .............................. 197
11.1.5 Error Phase ..................................... 198
11.1.6 Underlying Medium Service ........................ 198
11.2 Formalization .......................................... 198
11.2.1 Overall Structure ................................. 198
11.2.2 Sender/Receiver .................................. 200
11.2.3 Formalization of State Transitions .................. 202
12. AjG Specifications ....................................... 213
12.1 Simple Examples ....................................... 214
12.2 Semantics ............................................. 221
12.3 More Examples ........................................ 223
13. Memory with Locking .................................... 229
13.1 Black-Box Description .................................. 229
13.2 Distributed Implementation .............................. 234
14. Refinement ............................................... 241
14.1 Behavioral Refinement .................................. 242
14.2 Interface Refinement .................................... 242
14.3 Conditional Refinement ................................. 245
14.4 Verification ............................................ 247
14.5 Glass-Box Refinement ................................... 249
14.6 Development Method ........ , .......................... 250