Information systems for units and districts, are, in the terms of their functions, two different things. However, when looked at as a collection of data, they are only different aspects of a coherent interlocking of a number of systems, which deal with the same common set of data items. It is proposed therefore, in this chapter to discuss these two concepts as one, only defining a difference when this arises from a difference in use.

Information technology and its practical implementation is the ‘art of the realisable’. The question is not ‘can it be done?’, but ‘can it be done in good time without disproportionate cost?’. Current technology will allow complicated and extensive systems capable of serving any function or answering any question that an enthusiastic project board could conceive; however, most project boards work under constraints, of money if nothing else, so that systems as they are designed are a compromise in one or more aspects, e.g. functionality, performance, extent of implementation, etc.

Most systems are in existence as a response to a problem. They were not designed to solve that problem, they were retained for this purpose. The usual situation is that existing systems solved the last problem and have been adapted to deal with the present problems; with any luck they will do for the next set of problems.