Notes for a seminar: insights from a system specification aid

I describe an approach to specifying computing systems which shows promise as an aid in the design of systems for rehabilitation purposes. This approach has been developed as part of a continuing programme of investigation into the use of multiple communication channels in rehabilitation computing systems. When the work began ( 1988 ) there was little material on the design of computer systems for rehabilitation, and much evidence from the indifferent quality of some of the available software that design aids would be of value. It seemed clear that aids for design and specification could lead to better rehabilitation computing systems; here I advocate what appears to be a new approach to specification. Some earlier work is described in two reports, while the context of the study is set out in a previous note.The approach is directed primarily at computists as they develop designs for the computer component of a rehabilitation system. Clinical questions are not explicitly treated, and are assumed to have been settled before the technical design begins. ( That is not a requirement of the approach, and one would hope for interaction between clinical and technical design in practice, but the assumption gives a useful demarcation line for the discussion. )Why might we need special design techniques for rehabilitation systems ? At the level of detail, we don't, as there are already many tested methods for developing software from specifications --- although it would be encouraging to have rather more evidence that they are widely used. Composing the specifications is another matter, and here rehabilitation systems have two special features. First, the proper aim is communication, not merely character transmission; I shall discuss this point further. Second, we are commonly working with unconventional input or output equipment, where the computists' usual assumptions might not be appropriate. It is in these areas that the specification aid is effective.The approach is not ( yet ? ) a formal design technique. At present it is in the nature of a checklist, focusing attention on certain attributes of information handled in the system under consideration.