So far we've looked at fairly informal examples of sorting and arrangement – what might be done on a pragmatic basis and at a local level. One wouldn't expect the supermarket classification, or a rough arrangement of literature books, to be written down or distributed for others to use. The world is full of examples of this sort of local or personal classification; office filing systems are a typical example, as is any arrangement of the content of your kitchen cupboards or your wardrobe.

At a more public level there are a vast number of formal, published classifications of an immense variety of entities and phenomena. A search for ‘classification of ‘ using Google will return you in excess of 360 million sites. Among these are classifications for proteins, reptiles, disabilities, wetlands, daffodils, scorpions, depression, learning skills, theories of divine action, caviar, parachutes, subtle changes in facial expression, portable fire extinguishers, Bible commands, angles, thunderstorms, millionaires, chickens and tea.

Scientific classifications and taxonomies

For the most part these are classifications of different sorts of physical and biological entities, and they're constructed using the fundamental principles of grouping and ordering, which we discussed in Chapter 3, in a more extended, rigorous and systematic manner. The methodology they employ goes back to the Greek philosopher Aristotle, who, in the Organon, laid down the rules for creating categories of objects in the natural world. Aristotle produced the first classification for natural history, and the methods he used endure to the present day. He grouped natural phenomena (plants, birds, animals, people) into sets based on attributes or properties relating to their external appearance and behaviour, and he ordered these groups on the basis of their comparative similarity (or dissimilarity).

A classification of this kind is referred to as a taxonomy (from the Greek taxis meaning arrangement or order, and nomos, meaning law or rule). Although information managers often use the term taxonomy today to mean any vaguely structured set of terms in a subject area, taxonomy is a major scientific discipline with a highly developed, exact and complex methodology, usually supported by computational techniques.