Table Of ContentVolume 2: Essential Modeling Techniques
Structured
Development
for Real-Time
Systems
YOURDON COMPUTING SERIES
Ed Yourdon, Advisor
BENTON AND WEEKES Program It Right: A Structured Method in BASIC
BLOCK The Politics of Projects
BODDIE Crunch Mode: Building Effective Systems on a Tight Schedule
BRILL Building Controls Into Structured Systems
BRILL Techniques of EDP Project Management: A Book of Readings
CONSTANTINE AND YOURDON Structured Design: Fundamentals of a Discipline of
Computer Program and Systems Design
DE MARCO Concise Notes on Software Engineering
DE MARCO Controlling Software Projects: Management, Measurement, and Estimates
DE MARCO Structured Analysis and System Specification
DICKINSON Developing Structured Systems: A Methodology Using Structured
Techniques
FLAVIN Fundamental Concepts in Information Modeling
HANSEN Up and Running: A Case Study of Successful Systems Development
KELLER Expert Systems Technology: Development and Application
KELLER The Practice of Structured Analysis: Exploding Myths
KING Current Practices in Software Development: A Guide to Successful Systems
KRIEGER, POPPER, RIPPS, AND RADCLIFFE Structured Micro-Processor Programming
MAC DONALD Intuition to Implementation: Communicating About Systems Towards a
Language of Structure in Data Processing System Development
MC MENAMIN AND PALMER Essential Systems Analysis
ORR Structured Systems Development
PAGE-JONES The Practical Guide to Structured Systems Design
PETERS Software Design: Methods and Techniques
ROESKE The Data Factory: Data Center Operations and Systems Development
SEMPREVIO Teams in Information Systems Development
THOMSETT People and Project Management
WARD Systems Development Without Pain: A User's Guide to Modeling Organizational
Patterns
WARD AND MELLOR Structured Development for Real-Time Systems,
Volumes I, II, and III
WEAVER Using the Structured Techniques: A Case Study
WEINBERG Structured Analysis
WELLS A Structured Approach to Building Programs: BASIC
WELLS A Structured Approach to Building Programs: COBOL
WELLS A Structured Approach to Building Programs: Pascal
YOURDON Classics in Software Engineering
YOURDON Coming of Age in the Land of Computers
YOURDON Design of On-line Computer Systems
YOURDON, LISTER, GANE, AND SARSON Learning to Program in Structured Cobol, Parts
1 and 2
YOURDON Managing Structured Techniques, 31E
YOURDON Managing the System Life Cycle
YOURDON Structured Walkthroughs, 2IE
YOURDON Techniques of Program Structure and Design
YOURDON Writing of the Revolution: Selected Readings on Software Engineering
ZAHN C Notes: A Guide to the C Programming
Volume 2: Essential Modeling Techniques
Structured
Development
for Real-Time
Stephen J.MeUorSy stems
byPaulTWaidSc
YOURGDN PRESS
PRENTICE HALL BUILDING
A Pearson Education Company
Library of Congress Cataloging in Publication Data
Ward, Paul T.
Structured development for real-time systems.
Bibliography: v. 2, p.
Includes index
Contents: — v.2. Essential modeling techniques.
1. Real-time data processing. 2. System design.
3. Electronic data processing -- Structured techniques.
I. Mellor, Stephen J. II. Title.
QA76.54.W37 1985 005.1'13 85-50815
ISBN 0-13-854795-5 (pbk.: v.2)
20 19 18 17 16 15 14 13
© 1985 by Prentice-Hall, Inc.
A Pearson Education Company
Upper Saddle River, NJ 07458
All rights reserved. No part of this publication may be reproduced, stored in a retrieval
system, or transmitted, in any form or by any means, electronic, mechanical, photo-
copying, recording, or otherwise, without prior permission of the publisher.
Printed in the United States of America
Library of Congress Catalog Number 85-50815
ISBN 0-13-854795-5
This book was set in Times Roman by YOURDON Press, 1501 Broadway, New York,
N.Y., using a PDP-11/70 running under the UNIX* operating system.
*Unix is a registered trademark of Bell Laboratories.
Cover design by George Armstrong
Dedications
To Pamela with Love
- P.T.W.
To both my families
- S.J.M.
ACKNOWLEDGMENTS
We stated our gratefulness to various colleagues for contributions to the genesis
of our approach in the Acknowledgments for Volume 1, and we wish to reiterate our
gratefulness here.
We would particularly like to thank the technical reviewers of Volume 2 for their
hard work and for their helpful insights: Pete Coad, Jr., Charles S. Hendrickson, Peter
J. Gross, Steven Weiss, and W.K. Krutz.
A special word of thanks is due to John Shuttleworth of N.V. Philips. John was
the author of the original version of the SILLY case study, and generously permitted us
to include a version of the case study in this volume.
Finally, we wish to express our gratitude to Gerry Madigan and the Yourdon
Press editorial staff.
CONTENTS
Preface x
Introduction to Essential Modeling Heuristics Section xi
Note on Preliminary Edition xii
1. ESSENTIAL MODELING HEURISTICS 1
1.1 Introduction 1
1.2 Problems with functional decomposition 1
1.3 Environment-based modeling 3
1.4 Components of the total system 4
1.5 Subject-matter-centered modeling 6
1.6 Minimum-complexity representation 7
1.7 Summary 12
2. DEFINING SYSTEM CONTEXT 14
2.1 Introduction 14
2.2 Notation for context definition 14
2.3 Context definition in a systems engineering environment 16
2.4 Identification of terminators and flows 17
2.5 Exclusion of interface technology 19
2.6 Expanded contexts — material and energy transformations 21
2.7 Defining context specifics 24
2.8 Packaging context flows 26
2.9 Leveled and multiple-context schemas 26
2.10 Summary 27
3. MODELING EXTERNAL EVENTS 30
3.1 Introduction 30
3.2 Definition of an external event 30
3.3 Events versus event recognition 33
3.4 Identification of individual events 36
3.5 The active event modeling approach 36
3.6 The passive event modeling approach 37
3.7 The brainstorming approach to event modeling 38
3.8 Summary 39
4. DERIVING THE BEHAVIORAL MODEL 41
4.1 Introduction 41
4.2 An informal high-level requirements model 41
4.3 Systems dominated by a specific perspective 43
4.4 Representing behavior on the transformation schema 46
4.5 Regions of the transformation schema 47
vii
viii STRUCTURED DEVELOPMENT FOR REAL-TIME SYSTEMS
4.6 Classifying events 49
4.7 The preliminary transformation model 50
4.8 Constructing state-transition diagrams from an event list 50
4.9 Constructing data and control transformations from an event list 55
4.10 Constructing a data schema from an event list 59
4.11 Summary 60
5. COMPLETING THE ESSENTIAL MODEL - THE UPPER LEVELS 62
5.1 Introduction 62
5.2 Partitioning to minimize interfaces 63
5.3 Identifying hierarchies of control 66
5.4 Using response-related groupings 66
5.5 Using terminator-related groupings 69
5.6. Nameability of groupings 70
5.7 Summary 70
6. COMPLETING THE ESSENTIAL MODEL - THE LOWER LEVELS 71
6.1 Introduction 71
6.2 New development versus redevelopment 74
6.3 Extracting essential details from an existing implementation 75
6.4 Summary 78
7. ESSENTIAL MODEL TRACEABILITY 80
7.1 Introduction 80
7.2 Traceability between narrative requirements and the
environmental model 82
7.3 Traceability in the behavioral model 83
7.4 Use of tracing tables in the absence of a narrative 85
7.5 Documenattion of omissions from the model 85
7.6 Summary 86
APPENDIX A - CRUISE CONTROL SYSTEM 87
Problem Statement 88
Context Schema 90
Event List 91
Preliminary Transformation Schema 92
Leveled Set of Schemas 93
Data Dictionary 100
Transformation Specifications 102
CONTENTS ix
APPENDIX B - BOTTLE-FILLING SYSTEM 104
Problem Statement 105
Context Schema 107
Event List 108
Leveled Set of Schemas 109
Data Dictionary 115
Transformation Specifications 117
APPENDIX C - SILLY (Science and Industry Little Logic Yzer) 121
Problem Statement 122
Context Schema 124
Event List 125
Leveled Set of Schemas 127
Data Dictionary 131
Transformation Specifications 133
APPENDIX D - DEFECT INSPECTION SYSTEM 136
Problem Statement 137
Context Schema 139
Event List 140
Entity Relationship Diagram 141
Leveled Set of Diagrams 142
Data Dictionary 149
Transformation Specifications 153
INDEX 161
