The transformational implementation of JSD process specifications via finite automata representation

Conventional structured methods of software engineering are often based on the use of functional decomposition coupled with the Waterfall development process model. This approach is argued to be inadequate for coping with the evolutionary nature of large software systems. Alternative development paradigms, including the operational paradigm and the transformational paradigm, have been proposed to address the inadequacies of this conventional view of software developement, and these are reviewed. JSD is presented as an example of an operational approach to software engineering, and is contrasted with other well documented examples. The thesis shows how aspects of JSD can be characterised with reference to formal language theory and automata theory. In particular, it is noted that Jackson structure diagrams are equivalent to regular expressions and can be thought of as specifying corresponding finite automata. The thesis discusses the automatic transformation of structure diagrams into finite automata using an algorithm adapted from compiler theory, and then extends the technique to deal with areas of JSD which are not strictly formalisable in terms of regular languages. In particular, an elegant and novel method for dealing with so called recognition (or parsing) difficulties is described,. Various applications of the extended technique are described. They include a new method of automatically implementing the dismemberment transformation; an efficient way of implementing inversion in languages lacking a goto-statement; and a new in-the-large implementation strategy.

The debate on human automatism in mid-Victorian England

During the 1830s, Marshall Hall carried out innumerable experiments on a great variety of animals to establish the concept of a ‘reflex arc’. In France F.L.Goltz showed that decerebrate frogs were still capable of complex behaviours. Thomas Laycock in England and Ivan Sechenov in Russia sought to apply the reflex idea to the brain. This paper follows the debate in the periodical literature of mid-Victorian England and discusses the contributions of WB Carpenter, Herbert Spencer, TH Huxley, W Clifford and others. The previous outing of this issue in the post-Cartesian seventeenth century had been largely suppressed by ecclesiastical authority. In the nineteenth century ecclesiastical power had waned, at least in England, and the debate could take a more open form. As neurophysiology and behavioural science developed, with the widespread acceptance of Darwinian evolution, it became more and more difficult to deny that brain and mind were part of the natural world and subject to the usual laws of cause and effect. This, of course, had powerful implications for the human self-image and for jurisprudence. These implications are still with us and the work of neurophysiologists such as Benjamin Libet have only reinforced them. Should humans be regarded as ‘automata’ and, if so, what becomes of ‘free will’, ‘responsibility’, and the rule of law? The Victorian debate is still useful and relevant.

Enclosing the behavior of a hybrid automaton up to and beyond a Zeno point

Even simple hybrid automata like the classic bouncing ball can exhibit Zeno behavior. The existence of this type of behavior has so far forced a large class of simulators to either ignore some events or risk looping indefinitely. This in turn forces modelers to either insert ad-hoc restrictions to circumvent Zeno behavior or to abandon hybrid automata. To address this problem, we take a fresh look at event detection and localization. A key insight that emerges from this investigation is that an enclosure for a given time interval can be valid independent of the occurrence of a given event. Such an event can then even occur an unbounded number of times. This insight makes it possible to handle some types of Zeno behavior. If the post-Zeno state is defined explicitly in the given model of the hybrid automaton, the computed enclosure covers the corresponding trajectory that starts from the Zeno point through a restarted evolution.