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Transaction Specification for Object-Oriented Real-Time

Systems in HRT-HOOD

Pete Cornwell

Distributed Objects Research Group,
Department of Computing, Bournemouth University
Dorset, United Kingdom

Andy Wellings

Real-Time Systems Research Group
Department of Computer Science, University of York
York, United Kingdom

email: [email protected]

Object-oriented development is a structuring paradigm. It does not provide substantial support for the specification of 'end to end' control and data flow. This has implications for hard real-time system development, where applications may specify 'end to end' response times, also known as transactions. This paper introduces a graphical notation for the specification of transactions in HRT-HOOD, an object-oriented design technique for hard real-time system development. It provides an overview of the notation, and its practical application as part of a 'top-down' development process. This is illustrated through a case study, based on a naval command-control system.

1.0 Introduction

Object-based design of Ada programs has always been popular. Methods such as HRT-HOOD, HOOD and Boochs' OOD have been used to engineer a wide class of applications including hard real-time systems. One weakness of this technology is that it is primarily a structuring paradigm. Significant emphasis is placed on architectural structure to the detriment of 'end to end' control and data flow issues so important to real-time system design. In particular it is necessary to be able to design programs with 'end to end' response times, often called transactions. For example, reactive systems often have to respond to input within a given deadline; the computation required for that response might span across several (possibly distributed) objects. This interaction is not readily expressed in most object-based (or object-oriented) design methods.