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Capturing the temporal properties of complex systems : an evaluation of the timebands approach

The management and use of time is important to some extent in all systems. Be it simply the time between failures, the time to repair, the responsiveness to an operator’s demand, or the need for regular and frequent updates to the flight control surfaces of a fly-by-wire aircraft, time is a key parameter. Even though the times related to these characteristics span many orders of magnitude, from years at one extreme to milliseconds at the other, a range of 1012, the engineering techniques used to specify and capture the designs of these systems use one simple concrete notion of time — the second. In a discipline where abstraction is seen as being a key approach to the successful management of complexity, it appears paradoxical that there are no abstractions for time. This thesis argues that the provision of a banded abstraction of time supports better management, treatment and use of time. The application of such an abstraction as the primary focus for the architectural organisation of systems will ultimately result in systems of higher quality, ones which are more readily adapted to new roles, and can be more easily and predictably integrated into larger collaborations — systems-of-systems. Such improvements can reduce development timescales, resulting in the earlier availability of the final system; in time sensitive domains this early availability can ultimately lead to both commercial and strategic advantages. An existing timebands framework is the primary focus for this thesis. The major contributions of this thesis are to: • Extend the timebands framework in two ways: the addition of the concept of system modes; and the development of a process to identify and populate the bands of a system; • Provide an in-depth evaluation of the extended timebands framework through both an analysis of its definition, and its application in an industrial scale case study, demonstrating that its principles are sound, and that it has a clear role in the development of systems.