Question: Dan Tasker. Fourth Generation Data: A Guide to Data Analysis for New and Old Systems. Sydney, Australia: Prentice-Hall of Australia Pty., Ltd. (1989). A good pragmatic guide to database design, with the primary emphasis on individual data items. Data items are divided into three basic kinds: label, quantity, and description. Label items stand for entities; in relational terms, they correspond to primary and foreign keys. Quantity items represent amounts or measures or positions on a scale (possibly a date/time scale), and are subject to the usual arithmetic manipulations. Description items are all the rest. (Of course, there is much more to the classification scheme than this brief sketch can suggest.) The book goes on to deal with each kind in considerable detail. The discussions are not always "relationally pure"-for example, Taskers use of the term "domain" does not fully coincide with the relational use of that term-but the book does contain a great deal of sound practical advice.