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

331 Pages·1991·9.79 MB·English
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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. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher, Elsevier Science B.V., Copyright & Permissions Department, P.O. Box 521, 1000 AM Amsterdam, The Netherlands. Special regulations for readers in the U.S.A. - This publication has been registered with the Copyright Clearance Center Inc. (CCC), 222 Rosewood Drive, Danvers, MA 01932. Information can be obtained from the CCC about conditions under which photocopies of parts of this publication may be made in the U.S.A. All other copyright questions, including photocopying outside of the U.S.A., should be referred to the copyright owner, Elsevier Science B.V., unless otherwise specified. No responsibility is assumed by the publisher for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. This book is printed on acid-free paper. 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

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