HRT-HOOD: A Structured Design Method for Hard Real-Time Ada Systems (Real-Time Safety Critical Systems)

331 Pages·1991·9.79 MB·English

by  A. Burns, A. Wellings

HRT-HOOD™:
A Structured Design
Method for Hard
Real-Time Ada Systems
HRT-HOOD™:
A Structured Design
Method for Hard
Real-Time Ada Systems
REAL-TIME Series Editor:
SAFETY Hussein Zedan, Depar tment of Mathematics and Computat ional
Sciences, Liverpool John Moores University, Liverpool, U.K.
CRITICAL
SYSTEMS Vol. 1 Time and Probabil i ty in Formal Design of Distr ibuted Systems
(H.A. Hansson)
Vol. 2 Towards Verified Systems (J. Bowen, ed.)
Vol. 3 HRT-HOOD™: A Structured Design Method for H a r d
Real-Time Ada Systems ( A. Burns and A. Wellings)
REAL-TIME
HRT-HOOD™:
SAFETY
CRITICAL A Structured Design
SYSTEMS
Method for Hard
Real-Time Ada Systems
Alan Burns
Andy Wellings
Department of Computer Science
The University of York
Heslington, York, U.K.
MtOOD is a t rademark of the HOOD User Group
1995
ELSEVIER
AMSTERDAM • LAUSANNE • NEW YORK • OXFORD • SHANNON • TOKYO
ELSEVIER SCIENCE B.V.
Sara Burgerhartstraat 25
P.O. Box 211, 1000 AE Amsterdam, The Netherlands
ISBN: 0 444 82164 3
© 1995 Elsevier Science B.V. All rights reserved.
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Printed in The Netherlands.
Contents
Contents V
Foreword IX
Preface XI
Acknowledgements XI
Real-Time Systems Research at York XV
Part 1: Hard Real-Time HOD 1
Chapter 1: Overview of the HRT-HOD Design Proces 3
1.1 Introduction 3
1.2 The Importance of Non-Functional Requirements 5
1.3 The Software Development Life Cycle 6
1.4 Sumary 8
Chapter 2: Logical and Physical Architecture Design in HRT-HOOD 1
2.1 Logical Architecture Design 1
2.2 Physical Architecture Design 14
2.3 Sumary 18
Chapter 3: HRT-HOD Objects 19
3.1 Graphical Representation 19
3.2 Pasive Objects 21
3.3 Active Objects 21
3.4 Protected Objects 23
3.5 Cyclic Objects 24
3.6 Sporadic Objects 26
VI Contents
3.7 Real-Time Object Atributes 27
3.8 The Use Relationship (Control Flow) 29
3.9 The Include Relationship (Decomposition) 30
3.10 Operation Decomposition 31
3.1 Object Control Structure and Thread Decomposition 38
3.12 Data Flows 38
3.13 Exception Flows 3 8
3.14 Environment Objects 39
3.15 Clas Objects 40
3.16 Distributed Systems 42
3.17 Sumary 45
Part 2: Maping HRT-HOD Designs to Ada 47
Chapter 4: Suporting Hard Real-Time Systems in Ada 83 and Ada 95 49
4.1 The Ada 83 and Ada 95 Real-Time Models 50
4.2 Suporting Ada 95 Abstractions in Ada 83 51
4.3 Extending the Model 59
4.4 Implementation Cost 62
4.5 Sumary 64
Chapter 5: Overal Maping Aproach 65
5.1 HOD 3.1 to Ada 83 Maping 65
5.2 An Alternative Translation Aproach 68
5.3 Maping HRT-HOD to Ada 69
Chapter 6: Maping of Pasive and Active Objects 7
6.1 Pasive Terminal Objects 7
6.2 Active Terminal Objects 80
6.3 Clas and Instance Terminal Objects 91
Chapter 7: Maping Protected, Cyclic eind Sporadic Objects 93
7.1 Protected Terminal Objects 93
7.2 Cyclic Terminal Objects 10
7.3 Sporadic Terminal Objects 109
Chapter 8: Distributed Systems 129
8.1 Analysable Comunication Subsystem 131
8.2 Maping to Ada 95 136
8.3. Mapping Protected Objects in a Distributed Ada Environment 140
Contents VI
Part 3: Case Studies 143
Chapter 9: The Mine Control System 145
9.1 Mine Control System Overview 145
9.2 The Logical Architecture Design 150
9.3 The Physical Architecture Design 156
9.4 The Object Description Skeleton 160
9.5 Translation to Ada 95 201
9.6 Conclusion 24
Chapter 10: The Olympus Atitude and Orbital Control System 25
10.1 Background to the Case Study 25
10.2 The Modeled System: The Olympus AOCS 26
10.3 The Software Architecture Design 28
10.4 The Physical Architecture Design 242
10.5 Problems Encountered 24
10.6 Sumary 246
Chapter 1: Conclusions 247
Apendix A: Terminology 249
Apendix B: HRT-HOD Definition Rules 253
B.l Design Checking, Scoping and HRT-HOD Rules 253
B.2 General Definitions 25
B.3 Use Relationship 25
B.4 Include Relationships 256
B.5 Operations 256
B.6 Visibility 258
B.7 Consistency 258
Apendix C: Object Description Skeleton (ODS) Syntax Summary 261
C.l General Declarations 261
C.2 Object ODS Structure 262
C.3 The Visible Part of the ODS 263
C.4 The Hiden Part of the ODS 274
C.5 Parameters of Clas objects 280
Apendix D: Textual Formalism — the ODS Definition 281
D. 1 PASIVE Objects 281
D.2 ACTIVE Objects 284
VI Contents
D.3 PROTECTED Objects 287
D.4 CYCLIC Objects 290
D.5 SPORADIC Objects 295
D.6 ENVIRONMENT Objects 29
D.7 CLAS Objects 29
D.8 Instances of CLAS Objects 30
Apendix E: Device Control Objects in HRT-HOD 301
References 305
Index 31
IX
Foreword
The increasing use of computers for real-time control on board spacecrafts has bought
with it a greater emphasis on the development methodology used for such systems. By
their nature spacecraft control computers have to operate unattended for long periods and
because of the programmatics of space, systems are subject to a long development cycle.
As a result there are two distinct concerns, the first being that the development approach
guarantees functional and timing correctness, the second being that problems,
particularly those associated with timing, are considered as early as possible in the
spacecraft development life cycle.
The European Space Agency has, for a number of years, encouraged the
development of software using HOOD. It was thus a natural next step to investigate the
incorporation of time within the existing HOOD framework. This has proven to be very
beneficial, and this book describes the approach developed by the authors for handling
Hard Real-Time applications. It describes both the background scheduling theory,
provides practical examples of its application to real life problems, and demonstrates
how it is used in the various phases of the development of Hard-Real Time systems.
Thus I consider that HRT HOOD is a beneficial addition to the armoury of
techniques for developing real-time systems, and that this book is a welcome addition to
literature in this area which I can recommend for its insight and practical value.
Richard Creasey
European Space Research and Technology Centre