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HRT-HOOD: A Structured Design Method for Hard Real-Time Ada Systems

by Alan Burns and Andy Wellings

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Publication Details

Alan Burns and Andy Wellings
Hardback - 313 pages
ISBN: 0-444-82164-3

More information is also available from the publisher's catalogue.


For any set of application requirements there are potentially many system designs which can satisfy the required properties. A particular solution is usually arrived at by following a design method, either formally or informally. For hard real-time systems the situation is no different. The problem, however, is that current design methods do not adequately address the temporal characteristics of these systems. A hard real-time design method should guide the designer to a solution which can be analysed to ensure that the timing requirements have been met. The goal of this book is to present a structured design method which facilitates the construction and analysis of hard real-time systems. The book consists of three parts and five appendices.

Part 1: Hard Real-Time HOOD

Part 1 summarises our overall approach to the engineering of hard real-time systems, and indicates how the software development life cycle can be modified so that it addresses both functional and non-functional application requirements. Using the object-based framework, we identify the abstractions which must be available to the designer to guide the software development process towards the construction of predictable and analysable systems.

Part 2: Mapping HRT-HOOD to Ada

The overall goal of the project was to show how hard real-time systems can be designed and implemented in Ada. In Part 2 we show how HRT-HOOD designs can be systematically translated into Ada 95 and Ada 83.

Part 3: Case Studies

In this part of the book two case studies are presented. The first involves the control of a pump in a mine drainage system; it is a pedagogical study designed to illustrate many of the features available in HRT-HOOD. The second is the redesign of a real system so that the method can be evaluated. The system is the attitude and orbital control system for the Olympus Satellite.


  • Appendix A summarises the terminology used in this book.
  • Appendix B gives the rules which ensure that HRT-HOOD designs are consistent.
  • Appendix C defines the syntax of the Object Description Skeleton in a variant of Backus-Naur-Form.
  • Appendix D presents a more informal definition of the structure of an Object Description Skeleton.
  • Appendix E gives a definition of a device driver which is used in the mine drainage case study.