Taxonomies

Taxonomy (from Greek verb τασσειν or tassein = "to classify" and νομος or nomos = law, science, cf "economy") was once only the science of classifying living organisms (alpha taxonomy), but later the word was applied in a wider sense, and may also refer to either a classification of things, or the principles underlying the classification. Almost anything, animate objects, inanimate objects, places, and events, may be classified according to some taxonomic scheme.

Abstraction and hierarchy
Taxonomies are frequently hierarchical in structure, having parent child relationships. However, taxonomy may also refer to relationship schemes other than hierarchies, such as network structures.

Other taxonomies may include single children with multi-parents, for example, "Car" might appear with both parents "Vehicle" and "Steel Mechanisms"; to some however, this merely means that 'car' is part of several different taxonomies. A taxonomy might also be a simple organization of objects into groups, or even an alphabetical list. In current usage within "Knowledge Management", taxonomies are seen as slightly less broad than ontologies.

Mathematically, a hierarchical taxonomy is a tree structure of classifications for a given set of objects. At the top of this structure is a single classification, the root node, that applies to all objects. Nodes below this root are more specific classifications that apply to subsets of the total set of classified objects. So for instance in common schemes of scientific classification of organisms, the root is the Organism (as this applies to all living things, it is implied rather than stated explicitly). Below this are the Domain, Kingdom, Phylum (plural, phyla), Class, Order, Family, Genus, and Species, with various other ranks sometimes inserted.

Taxonomy and mental classification
Some have argued that the human mind naturally organizes its knowledge of the world into such systems. This view is often based on the epistemology of Immanuel Kant. Anthropologists have observed that taxonomies are generally embedded in local cultural and social systems, and serve various social functions. Perhaps the most well-known and influential study of folk taxonomies is Émile Durkheim's The Elementary Forms of Religious Life. The theories of Kant and Durkheim also influenced Claude Lévi-Strauss, the founder of anthropological structuralism. Lévi-Strauss wrote two important books on taxonomies, Totemism and The Savage Mind.

Other uses
Such taxonomies as those analyzed by Durkheim and Lévi-Strauss are sometimes called folk taxonomies to distinguish them from scientific taxonomies that claim to be disembedded from social relations and thus objective and universal.

A recent neologism, folksonomy, should not be confused with Folk Taxonomy (though it is obviously a contraction of the two words). Those who support scientific taxonomies have recently criticized folksonomies by dubbing them fauxonomies.

The phrase enterprise taxonomy is used in business to describe a very limited form of taxonomy used only within one organization.

The field of solving or best-fitting of numerical equations that characterize all measurable quantities of a set of objects is called cluster analysis; this is a form of taxonomy called numerical taxonomy or taximetrics.