Taxonomies

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Taxonomy is the practice and science of classification. The word comes from the Greek τάξις, taxis, 'order' + νόμος, nomos, 'law' or 'science'. Taxonomies, or taxonomic schemes, are composed of taxonomic units known as taxa (singular taxon), or kinds of things that are arranged frequently in a hierarchical structure, typically related by subtype-supertype relationships, also called parent-child relationships. In such a subtype-supertype relationship the subtype kind of thing has by definition the same constraints as the supertype kind of thing plus one or more additional constraints. For example, car is a subtype of vehicle. So any car is also a vehicle, but not every vehicle is a car. So, a thing needs to satisfy more constraints to be a car than to be a vehicle.

Applications

Originally the term taxonomy referred to the classifying of living organisms (now known as alpha taxonomy); however, the term is now applied in a wider, more general sense and now may refer to a classification of things, as well as to the principles underlying such a classification.

Almost anything — animate objects, inanimate objects, places, concepts, events, properties, and relationships — may be classified according to some taxonomic scheme.

The term taxonomy may also apply to relationship schemes other than parent-child hierarchies, such as network structures with other types of relationships. 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 a part of several different taxonomies.

A taxonomy might also be a simple organization of kinds of things into groups, or even an alphabetical list. However, the term vocabulary is more appropriate for such a list. In current usage within "Knowledge Management", taxonomies are seen as less broad than ontologies as ontologies apply a larger variety of relation types.

Mathematically, a hierarchical taxonomy is a tree structure of classifications for a given set of objects. It is also named Containment hierarchy. 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 called "Organism" followed by nodes for the taxonomic ranks: Domain, kingdom, phylum, class, etc.

Taxonomy and mental classification

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. A more recent treatment of folk taxonomies (including the results of several decades of empirical research) and the discussion of their relation to the scientific taxonomy can be found in Scott Atran's Cognitive Foundations of Natural History. Folk taxonomies of organisms have been found in large part to agree with scientific classification, at least for the larger and more obvious species, which means that it is not the case that folk taxonomies are based purely on utilitarian characteristics.

In the seventeenth century the German mathematician and philosopher Gottfried Leibniz, following the work of the thirteenth-century Majorcan philosopher Ramon Llull on his Ars generalis ultima, a system for procedurally generating concepts by combining a fixed set of ideas, sought to develop an alphabet of human thought. Leibniz intended his characteristica universalis to be an "algebra" capable of expressing all conceptual thought. The concept of creating such a "universal language" was frequently examined in the seventeenth century, also notably by the English philosopher John Wilkins in his work An Essay towards a Real Character and a Philosophical Language (1668), from which the classification scheme in Roget's Thesaurus ultimately derives.

Is-a and Has-a relationships

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Two of the predominant types of relationships in knowledge-representation systems are predication and the universally quantified conditional. Predication relationships express the notion that an individual entity is an example of a certain type (for example, John is a bachelor), while universally quantified conditionals express the notion that a type is a subtype of another type (for example, A dog is a mammal).

Various taxonomies

In Psychology

Here are a number of taxonomies or lists of significant clinical phenomena:

• CAT Traps

• CAT Snags

• Defence mechanisms

• Psychodiagnostic typologies

• Schema Therapy Schemas

In phylogenetic taxonomy (or cladistic taxonomy), organisms can be classified by clades, which are based on evolutionary grouping by ancestral traits. By using clades as the criteria for separation, cladistic taxonomy, using cladograms, can categorize taxa into unranked groups.

In numerical taxonomy or taximetrics, the field of solving or best-fitting of numerical equations that characterize all measurable quantities of a set of objects is called cluster analysis.

Non-scientific taxonomy

Other taxonomies, such 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.

See also

• Attribute-value system
• Carolus Linnaeus, the father of modern taxonomy
• Cladistics, the most prominent of several forms of phylogenetic systematics
• Ethnotaxonomy
• Folksonomy
• Lexicon
• Knowledge representation
• Nosology
• Ontology,
• Semantic network
• Scientific classification
• Structuralism
• Systematics
• Taxonomic classification
• Taxonomic rank
• Taxonomy of education objectives
• Taxonomies in therapy
• Taxonomy (biology)

External links

• Wikispecies Main Page
• Taxonomy Browser of National Center for Biotechnology Information