There is as yet no unified theory of retrieval systems, and a good deal of retrieval practice is still an empirical art, unsullied by theory. - Brian Campbell Vickery

The areas traditionally concerned with such systems are: publishing in all its ramification, librarianship, bibliography, documentation, record management, archives and the like. Systematic study of the activities in all these areas has lead to increased recognition of their common features. They are all concerned with information systems, and their study may include in the wider field of 'information science and technology' (as the Americans put it) or 'informatics' (as Soviet writers would have it).

[There has been] a widening of the field covered by the concept of “information”, both its theory and its practice. Information transfer has been put on a par with the transfer of matter and energy, as one of the primary natural processes.’

Systems transfer or transform materials, energy or information - and usually all three. An information system is one whose prime function is to transfer or transform information: the telephone system is an obvious example. This book concentrates on certain types of information system: those concerned with the transfer of information between specialists, mainly with reference to their work, and mainly based on documents. The focus is thus on specialised documentary information systems.