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280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme of classes (a taxonomy) and the allocation of things to the classes (
classification Classification is the activity of assigning objects to some pre-existing classes or categories. This is distinct from the task of establishing the classes themselves (for example through cluster analysis). Examples include diagnostic tests, identif ...
). Originally, taxonomy referred only to the classification of organisms on the basis of shared characteristics. Today it also has a more general sense. It may refer to the classification of things or concepts, as well as to the principles underlying such work. Thus a taxonomy can be used to organize species, documents, videos or anything else. A taxonomy organizes taxonomic units known as "taxa" (singular "taxon"). Many are hierarchies. One function of a taxonomy is to help users more easily find what they are searching for. This may be effected in ways that include a library classification system and a search engine taxonomy.


Etymology

The word was coined in 1813 by the Swiss botanist A. P. de Candolle and is irregularly compounded from the Greek , ''taxis'' 'order' and , ''nomos'' 'law', connected by the French form ; the regular form would be ', as used in the Greek reborrowing .


Applications

Wikipedia categories form a taxonomy, which can be extracted by automatic means. , it has been shown that a manually-constructed taxonomy, such as that of computational lexicons like
WordNet WordNet is a lexical database of semantic relations between words that links words into semantic relations including synonyms, hyponyms, and meronyms. The synonyms are grouped into ''synsets'' with short definitions and usage examples. It can thu ...
, can be used to improve and restructure the Wikipedia category taxonomy. In a broader sense, taxonomy also applies to relationship schemes other than parent-child hierarchies, such as network structures. Taxonomies may then include a single child 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 simply be organization of kinds of things into groups, or an alphabetical list; here, however, the term vocabulary is more appropriate. In current usage within
knowledge management Knowledge management (KM) is the set of procedures for producing, disseminating, utilizing, and overseeing an organization's knowledge and data. It alludes to a multidisciplinary strategy that maximizes knowledge utilization to accomplish organ ...
, taxonomies are considered narrower than
ontologies In information science, an ontology encompasses a representation, formal naming, and definitions of the categories, properties, and relations between the concepts, data, or entities that pertain to one, many, or all domains of discourse. More ...
since ontologies apply a larger variety of relation types. Mathematically, a hierarchical taxonomy is a
tree structure A tree structure, tree diagram, or tree model is a way of representing the hierarchical nature of a structure in a graphical form. It is named a "tree structure" because the classic representation resembles a tree, although the chart is gen ...
of classifications for a given set of objects. It is also named
containment hierarchy A hierarchy (from Greek: , from , 'president of sacred rites') is an arrangement of items (objects, names, values, categories, etc.) that are represented as being "above", "below", or "at the same level as" one another. Hierarchy is an importan ...
. 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. The progress of reasoning proceeds from the general to the more specific. By contrast, in the context of legal terminology, an open-ended contextual taxonomy is employed—a taxonomy holding only with respect to a specific context. In scenarios taken from the legal domain, a formal account of the open-texture of legal terms is modeled, which suggests varying notions of the "core" and "penumbra" of the meanings of a concept. The progress of reasoning proceeds from the specific to the more general.


History

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 David Émile Durkheim (; or ; 15 April 1858 – 15 November 1917) was a French Sociology, sociologist. Durkheim formally established the academic discipline of sociology and is commonly cited as one of the principal architects of modern soci ...
'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 Gottfried Wilhelm Leibniz (or Leibnitz; – 14 November 1716) was a German polymath active as a mathematician, philosopher, scientist and diplomat who is credited, alongside Isaac Newton, Sir Isaac Newton, with the creation of calculus in ad ...
, following the work of the thirteenth-century Majorcan philosopher
Ramon Llull Ramon Llull (; ; – 1316), sometimes anglicized as ''Raymond Lully'', was a philosopher, theologian, poet, missionary, Christian apologist and former knight from the Kingdom of Majorca. He invented a philosophical system known as the ''Art ...
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 The Latin term ''characteristica universalis'', commonly interpreted as ''universal characteristic'', or ''universal character'' in English, is a universal and formal language imagined by Gottfried Leibniz able to express mathematical, scienti ...
'' to be an "algebra" capable of expressing all conceptual thought. The concept of creating such a " universal language" was frequently examined in the 17th century, also notably by the English philosopher John Wilkins in his work ''
An Essay towards a Real Character and a Philosophical Language ''An Essay Towards a Real Character, and a Philosophical Language'' (London, 1668) is the best-remembered of the numerous works of John Wilkins, in which he expounds a new universal language, meant primarily to facilitate international communica ...
'' (1668), from which the classification scheme in Roget's
Thesaurus A thesaurus (: thesauri or thesauruses), sometimes called a synonym dictionary or dictionary of synonyms, is a reference work which arranges words by their meanings (or in simpler terms, a book where one can find different words with similar me ...
ultimately derives.


Taxonomy in various disciplines


Natural sciences

Taxonomy in biology encompasses the description, identification, nomenclature, and classification of organisms. Uses of taxonomy include: *
Alpha taxonomy In biology, taxonomy () is the science, scientific study of naming, defining (Circumscription (taxonomy), circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxon, taxa (si ...
, the description and basic classification of new species, subspecies, and other taxa **
Linnaean taxonomy Linnaean taxonomy can mean either of two related concepts: # The particular form of biological classification (taxonomy) set up by Carl Linnaeus, as set forth in his ''Systema Naturae'' (1735) and subsequent works. In the taxonomy of Linnaeus th ...
, the original classification scheme of Carl Linnaeus ** rank-based scientific classification as opposed to clade-based classification * Evolutionary taxonomy, traditional post-Darwinian hierarchical biological classification *
Numerical taxonomy Numerical taxonomy is a classification system in biological systematics which deals with the grouping by numerical methods of taxonomic units based on their character states. It aims to create a taxonomy using numeric algorithms like cluster an ...
, various taxonomic methods employing numeric algorithms *
Phenetics In biology, phenetics (; ), also known as taximetrics, is an attempt to classify organisms based on overall similarity, usually with respect to morphology or other observable traits, regardless of their phylogeny or evolutionary relation. It is ...
, system for ordering species based on overall similarity *
Phylogenetics In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
, biological taxonomy based on putative ancestral descent of organisms *
Plant taxonomy Plant taxonomy is the science that finds, identifies, describes, classifies, and names plants. It is one of the main branches of taxonomy (the science that finds, describes, classifies, and names living things). Plant taxonomy is closely allied ...
*
Virus classification Virus classification is the process of naming viruses and placing them into a taxonomy (biology), taxonomic system similar to the classification systems used for cell (biology), cellular organisms. Viruses are classified by phenotypic characteri ...
, taxonomic system for viruses *
Folk taxonomy A folk taxonomy is a vernacular name, naming system, as distinct from Taxonomy (general), scientific taxonomy. Folk biological classification is the way people traditionally describe and organize the world around them, typically making generous us ...
, description and organization, by individuals or groups, of their own environments *
Nosology Nosology () is the branch of medical science that deals with the classification of diseases. Fully classifying a medical condition requires knowing its cause (and that there is only one cause), the effects it has on the body, the symptoms th ...
, classification of diseases * Soil classification, systematic categorization of soils


Business and economics

Uses of taxonomy in business and economics include: *
Corporate taxonomy Corporate taxonomy is the hierarchical classification of entities of interest of an enterprise, organization or administration, used to classify documents, digital assets and other information. Taxonomies can cover virtually any type of physical or ...
, the hierarchical classification of entities of interest to an enterprise, organization or administration *
Economic taxonomy An economic taxonomy is a system of classification of economic activity, including products, companies and industries. Some economists believe that the study of economic policy demands the use of a taxonomic/classificatory approach. Industry taxon ...
, a system of classification for economic activity ** Global Industry Classification Standard, an industry taxonomy developed by MSCI and Standard & Poor's (S&P) ** Industry Classification Benchmark, an industry classification taxonomy launched by Dow Jones and FTSE **
International Standard Industrial Classification The International Standard Industrial Classification of All Economic Activities (ISIC) is a United Nations industry classification system. Wide use has been made of ISIC in classifying data according to kind of economic activity in the fields of em ...
(ISIC), a United Nations system for classifying economic data **
North American Industry Classification System The North American Industry Classification System or NAICS () is a industry classification, classification of business establishments by type of economic activity (the process of production). It is used by governments and business in Canada, Mexic ...
(NAICS), used in Canada, Mexico, and the United States of America ** Pavitt's Taxonomy, classification of firms by their principal sources of innovation ** Standard Industrial Classification, a system for classifying industries by a four-digit code ** United Kingdom Standard Industrial Classification of Economic Activities, a Standard Industrial Classification by type of economic activity * EU taxonomy for sustainable activities, a classification system established to clarify which investments are environmentally sustainable, in the context of the European Green Deal. * Records management taxonomy, the representation of data, upon which the classification of unstructured content is based, within an organization. * XBRL Taxonomy, eXtensible Business Reporting Language * SRK taxonomy, in workplace user-interface design


Computing


Software engineering

Vegas et al. make a compelling case to advance the knowledge in the field of software engineering through the use of taxonomies. Similarly, Ore et al. provide a systematic methodology to approach taxonomy building in software engineering related topics. Several taxonomies have been proposed in software testing research to classify techniques, tools, concepts and artifacts. The following are some example taxonomies: # A taxonomy of model-based testing techniques # A taxonomy of static-code analysis tools Engström et al. suggest and evaluate the use of a taxonomy to bridge the communication between researchers and practitioners engaged in the area of software testing. They have also developed a web-based tool to facilitate and encourage the use of the taxonomy. The tool and its source code are available for public use.


Other uses of taxonomy in computing

*
Flynn's taxonomy Flynn's taxonomy is a classification of computer architectures, proposed by Michael J. Flynn in 1966 and extended in 1972. The classification system has stuck, and it has been used as a tool in the design of modern processors and their functionalit ...
, a classification for instruction-level parallelism methods *
Folksonomy Folksonomy is a classification system in which end users apply public tags to online items, typically to make those items easier for themselves or others to find later. Over time, this can give rise to a classification system based on those tag ...
, classification based on user's tags *
Taxonomy for search engines Taxonomy for search engines refers to classification methods that improve relevance in vertical search. Taxonomies of entities are tree structures whose nodes are labelled with entities likely to occur in a web search query. Searches use these tre ...
, considered as a tool to improve relevance of search within a vertical domain * ACM Computing Classification System, a subject classification system for computing devised by the Association for Computing Machinery


Education and academia

Uses of taxonomy in education include: *
Bloom's taxonomy Bloom's taxonomy is a framework for categorizing Educational aims and objectives, educational goals, developed by a committee of educators chaired by Benjamin Bloom in 1956. It was first introduced in the publication ''Taxonomy of Educational Obje ...
, a standardized categorization of learning objectives in an educational context * Classification of Instructional Programs, a taxonomy of academic disciplines at institutions of higher education in the United States *
Mathematics Subject Classification The Mathematics Subject Classification (MSC) is an alphanumerical classification scheme that has collaboratively been produced by staff of, and based on the coverage of, the two major mathematical reviewing databases, Mathematical Reviews and Zen ...
, an alphanumerical classification scheme based on the coverage of Mathematical Reviews and Zentralblatt MATH * SOLO taxonomy, Structure of Observed Learning Outcome, proposed by Biggs and Collis Tax


Safety

Uses of taxonomy in safety include: * Safety taxonomy, a standardized set of terminologies used within the fields of safety and health care ** Human Factors Analysis and Classification System, a system to identify the human causes of an accident ** Swiss cheese model, a model used in risk analysis and risk management propounded by Dante Orlandella and James T. Reason **A taxonomy of rail incidents in Confidential Incident Reporting & Analysis System (CIRAS)


Other taxonomies

* Military taxonomy, a set of terms that describe various types of military operations and equipment * Moys Classification Scheme, a subject classification for law devised by Elizabeth Moys


Research publishing

Citing inadequacies with current practices in listing authors of papers in medical research journals, Drummond Rennie and co-authors called in a 1997 article in ''JAMA'', the ''
Journal of the American Medical Association ''JAMA'' (''The Journal of the American Medical Association'') is a peer-reviewed medical journal published 48 times a year by the American Medical Association. It publishes original research, reviews, and editorials covering all aspects of ...
'' for
''a radical conceptual and systematic change, to reflect the realities of multiple authorship and to buttress accountability. We propose dropping the outmoded notion of author in favor of the more useful and realistic one of contributor.''
In 2012, several major academic and scientific publishing bodies mounted ''Project CRediT'' to develop a
controlled vocabulary A controlled vocabulary provides a way to organize knowledge for subsequent retrieval. Controlled vocabularies are used in subject indexing schemes, subject headings, thesauri, taxonomies and other knowledge organization systems. Controlled v ...
of contributor roles. Known as ''CRediT ( Contributor Roles Taxonomy)'', this is an example of a flat, non-hierarchical taxonomy; however, it does include an optional, broad classification of the degree of contribution: ''lead'', ''equal'' or ''supporting''. Amy Brand and co-authors summarise their intended outcome as:
Identifying specific contributions to published research will lead to appropriate credit, fewer author disputes, and fewer disincentives to collaboration and the sharing of data and code.
CRediT comprises 14 specific contributor roles using the following defined terms: *Conceptualization *Methodology *Software *Validation *Formal Analysis *Investigation *Resources *Data curation *Writing – Original Draft *Writing – Review & Editing *Visualization *Supervision *Project Administration *Funding acquisition The taxonomy is an open standard conformiing to the OpenStand principles, and is published under a
Creative Commons Creative Commons (CC) is an American non-profit organization and international network devoted to educational access and expanding the range of creative works available for others to build upon legally and to share. The organization has release ...
licence.


Taxonomy for the web

Websites with a well designed taxonomy or hierarchy are easily understood by users, due to the possibility of users developing a mental model of the site structure. Guidelines for writing taxonomy for the web include: * Mutually exclusive categories can be beneficial. If categories appear in several places, it is called cross-listing or polyhierarchical. The hierarchy will lose its value if cross-listing appears too often. Cross-listing often appears when working with ambiguous categories that fits more than one place. * Having a balance between breadth and depth in the taxonomy is beneficial. Too many options (breadth), will overload the users by giving them too many choices. At the same time having a too narrow structure, with more than two or three levels to click-through, will make users frustrated and might give up.


In communications theory

Frederick SuppeSuppe, Frederick. 1989. "Classification". In Erik Barnouw ed., International encyclopedia of communications. Oxford, UK: Oxford University Press, vol. 1, 292-296 distinguished two senses of classification: a broad meaning, which he called "conceptual classification" and a narrow meaning, which he called "systematic classification". About conceptual classification Suppe wrote: "Classification is intrinsic to the use of language, hence to most if not all communication. Whenever we use nominative phrases we are classifying the designated subject as being importantly similar to other entities bearing the same designation; that is, we classify them together. Similarly the use of predicative phrases classifies actions or properties as being of a particular kind. We call this conceptual classification, since it refers to the classification involved in conceptualizing our experiences and surroundings" About systematic classification Suppe wrote: "A second, narrower sense of classification is the systematic classification involved in the design and utilization of taxonomic schemes such as the biological classification of animals and plants by genus and species.


Is-a and has-a relationships, and hyponymy

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"'', which means the same as "''All dogs are mammals"''). Ronald J. Brachman
What IS-A is and isn't. An Analysis of Taxonomic Links in Semantic Networks
. IEEE Computer, 16 (10); October 1983.
The "has-a" relationship is quite different: an elephant ''has'' a trunk; a trunk is a part, not a subtype of elephant. The study of part-whole relationships is
mereology Mereology (; from Greek μέρος 'part' (root: μερε-, ''mere-'') and the suffix ''-logy'', 'study, discussion, science') is the philosophical study of part-whole relationships, also called ''parthood relationships''. As a branch of metaphys ...
. Taxonomies are often represented as ''is-a'' hierarchies where each level is more specific than the level above it (in mathematical language is "a subset of" the level above). For example, a basic biology taxonomy would have concepts such as ''mammal'', which is a subset of ''animal'', and ''dogs'' and ''cats'', which are subsets of ''mammal''. This kind of taxonomy is called an is-a model because the specific objects are considered as instances of a concept. For example, ''Fido'' is-an instance of the concept ''dog'' and ''Fluffy'' is-a ''cat''.
In
linguistics Linguistics is the scientific study of language. The areas of linguistic analysis are syntax (rules governing the structure of sentences), semantics (meaning), Morphology (linguistics), morphology (structure of words), phonetics (speech sounds ...
, is-a relations are called
hyponymy Hypernymy and hyponymy are the wikt:Wiktionary:Semantic relations, semantic relations between a generic term (''hypernym'') and a more specific term (''hyponym''). The hypernym is also called a ''supertype'', ''umbrella term'', or ''blanket term ...
. When one word describes a category, but another describe some subset of that category, the larger term is called a ''hypernym'' with respect to the smaller, and the smaller is called a "hyponym" with respect to the larger. Such a hyponym, in turn, may have further subcategories for which it is a hypernym. In the simple biology example, ''dog'' is a hypernym with respect to its subcategory ''collie'', which in turn is a hypernym with respect to ''Fido'' which is one of its hyponyms. Typically, however, ''hypernym'' is used to refer to subcategories rather than single individuals.


Research

Researchers reported that large populations consistently develop highly similar category systems. This may be relevant to lexical aspects of large communication networks and cultures such as folksonomies and
language Language is a structured system of communication that consists of grammar and vocabulary. It is the primary means by which humans convey meaning, both in spoken and signed language, signed forms, and may also be conveyed through writing syste ...
or human communication, and sense-making in general.


Theoretical approaches


Knowledge organization

Hull (1998) suggested "The fundamental elements of any classification are its theoretical commitments, basic units and the criteria for ordering these basic units into a classification".Hull, David L. 1998. “Taxonomy.” In Routledge Encyclopedia of Philosophy, ed. Edward Craig. London: Routledge 9: 272-76. There is a widespread opinion in knowledge organization and related fields that such classes corresponds to concepts. We can, for example, classify "waterfowls" into the classes "ducks", "geese", and "swans"; we can also say, however, that the concept “waterfowl” is a generic broader term in relation to the concepts "ducks", "geese", and "swans". This example demonstrates the close relationship between classification theory and concept theory. A main opponent of concepts as units is Barry Smith. Arp, Smith and Spear (2015) discuss ontologies and criticize the conceptualist understanding. The book writes (7): “The code assigned to France, for example, is ISO 3166 – 2:FR and the code is assigned to France itself — to the country that is otherwise referred to as Frankreich or Ranska. It is not assigned to the concept of France (whatever that might be).” Smith's alternative to concepts as units is based on a realist orientation, when scientists make successful claims about the types of entities that exist in reality, they are referring to objectively existing entities which realist philosophers call universals or natural kinds. Smith's main argument - with which many followers of the concept theory agree - seems to be that classes cannot be determined by introspective methods, but must be based on scientific and scholarly research. Whether units are called concepts or universals, the problem is to decide when a thing (say a "blackbird") should be considered a natural class. In the case of blackbirds, for example, recent DNA analysis have reconsidered the concept (or universal) "blackbird" and found that what was formerly considered one species (with subspecies) are in reality many different species, which just have chosen similar characteristics to adopt to their ecological niches. An important argument for considering concepts the basis of classification is that concepts are subject to change and that they change when scientific revolutions occur. Our concepts of many birds, for example, have changed with recent development in DNA analysis and the influence of the cladistic paradigm - and have demanded new classifications. Smith's example of ''France'' demands an explanation. First, ''France'' is not a general concept, but an individual concept. Next, the legal definition of France is determined by the conventions that France has made with other countries. It is still a concept, however, as Leclercq (1978) demonstrates with the corresponding concept ''Europe''. Hull (1998) continued: "Two fundamentally different sorts of classification are those that reflect structural organization and those that are systematically related to historical development." What is referred to is that in biological classification the anatomical traits of organisms is one kind of classification, the classification in relation to the evolution of species is another (in the section below, we expand these two fundamental sorts of classification to four). Hull adds that in biological classification, evolution supplies the theoretical orientation.


Ereshevsky

Ereshefsky (2000) presented and discussed three general philosophical schools of classification: "essentialism, cluster analysis, and historical classification. Essentialism sorts entities according to causal relations rather than their intrinsic qualitative features." These three categories may, however, be considered parts of broader philosophies. Four main approaches to classification may be distinguished: (1) logical and rationalist approaches including "essentialism"; (2) empiricist approaches including cluster analysis. (It is important to notice that empiricism is not the same as empirical study, but a certain ideal of doing empirical studies. With the exception of the logical approaches they all are based on empirical studies, but are basing their studies on different philosophical principles). (3) Historical and hermeneutical approaches including Ereshefsky's "historical classification" and (4) Pragmatic, functionalist and teleological approaches (not covered by Ereshefsky). In addition, there are combined approaches (e.g., the so-called evolutionary taxonomy", which mixes historical and empiricist principles).


Logical and rationalist approaches

Logical division, or ''logical partitioning'' (top-down classification or downward classification) is an approach that divides a class into subclasses and then divide subclasses into their subclasses, and so on, which finally forms a tree of classes. The root of the tree is the original class, and the leaves of the tree are the final classes.
Plato Plato ( ; Greek language, Greek: , ; born  BC, died 348/347 BC) was an ancient Greek philosopher of the Classical Greece, Classical period who is considered a foundational thinker in Western philosophy and an innovator of the writte ...
advocated a method based on dichotomy, which was rejected by
Aristotle Aristotle (; 384–322 BC) was an Ancient Greek philosophy, Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, a ...
and replaced by the method of definitions based on genus, species, and specific difference. The method of facet analysis (cf., faceted classification) is primarily based on logical division. This approach tends to classify according to "essential" characteristics, a widely discussed and criticized concept (cf.,
essentialism Essentialism is the view that objects have a set of attributes that are necessary to their Identity (philosophy), identity. In early Western thought, Platonic idealism held that all things have such an "essence"—an Theory of forms, "idea" or "f ...
). These methods may overall be related to the rationalist theory of knowledge. Michelle Bunn notes that logical partitioning uses categories which are established ''
a priori ('from the earlier') and ('from the later') are Latin phrases used in philosophy to distinguish types of knowledge, Justification (epistemology), justification, or argument by their reliance on experience. knowledge is independent from any ...
''; data is then collected and used to test the extent to which the classification system can be sustained.


Empiricist approaches

"Empiricism alone is not enough: a healthy advance in taxonomy depends on a sound theoretical foundation"
Phenetics In biology, phenetics (; ), also known as taximetrics, is an attempt to classify organisms based on overall similarity, usually with respect to morphology or other observable traits, regardless of their phylogeny or evolutionary relation. It is ...
or
numerical taxonomy Numerical taxonomy is a classification system in biological systematics which deals with the grouping by numerical methods of taxonomic units based on their character states. It aims to create a taxonomy using numeric algorithms like cluster an ...
is by contrast bottom-up classification, where the starting point is a set of items or individuals, which are classified by putting those with shared characteristics as members of a narrow class and proceeding upward. Numerical taxonomy is an approach based solely on observable, measurable similarities and differences of the things to be classified. Classification is based on overall similarity: the elements that are most alike in most attributes are classified together. But it is based on statistics, and therefore does not fulfill the criteria of logical division (e.g. to produce classes, that are mutually exclusive and jointly coextensive with the class they divide). Some people will argue that this is not classification/taxonomy at all, but such an argument must consider the definitions of classification (see above). These methods may overall be related to the empiricist theory of knowledge.


Historical and hermeneutical approaches

Genealogical classification is classification of items according to their common heritage. This must also be done on the basis of some empirical characteristics, but these characteristics are developed by the theory of evolution. Charles Darwin's main contribution to classification theory was not just his claim "... all true classification is genealogical ..." but that he provided operational guidance for classification. Genealogical classification is not restricted to biology, but is also much used in, for example, classification of languages, and may be considered a general approach to classification." These methods may overall be related to the historicist theory of knowledge. One of the main schools of historical classification is
cladistics Cladistics ( ; from Ancient Greek 'branch') is an approach to Taxonomy (biology), biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesiz ...
, which is today dominant in biological taxonomy, but also applied to other domains. The historical and hermeneutical approaches is not restricted to the development of the object of classification (e.g., animal species) but is also concerned with the subject of classification (the classifiers) and their embeddedness in scientific traditions and other human cultures.


Pragmatic, functionalist and teleological approaches

Pragmatic classification (and functionalBonaccorsi, Andres, Gualtiero Fantoni, Riccardo Apreda and Donata Gabelloni. 2019. “Functional Patent Classification”. In ''Springer Handbook of Science and Technology Indicators'', eds. Wolfgang Glänzel, Henk F. Moed, Ulrich Schmoch and Mike Thelwall. Cham, Switzerland : Springer, Chapter 40: 983-1003. and teleological classification) is the classification of items which emphasis the goals, purposes, consequences, interests, values and politics of classification. It is, for example, classifying animals into wild animals, pests, domesticated animals and pets. Also kitchenware (tools, utensils, appliances, dishes, and cookware used in food preparation, or the serving of food) is an example of a classification which is not based on any of the above-mentioned three methods, but clearly on pragmatic or functional criteria. Bonaccorsi, et al. (2019) is about the general theory of functional classification and applications of this approach for patent classification. Although the examples may suggest that pragmatic classifications are primitive compared to established scientific classifications, it must be considered in relation to the pragmatic and critical theory of knowledge, which consider all knowledge as influences by interests. Ridley (1986) wrote:Ridley, Mark. 1986. ''Evolution and Classification: The Reformation of Cladism''. London: Longman. "teleological classification. Classification of groups by their shared purposes, or functions, in life - where purpose can be identified with adaptation. An imperfectly worked-out, occasionally suggested, theoretically possible principle of classification that differs from the two main such principles, ''phenetic'' and ''phylogenetic classification''".


Artificial versus natural classification

Natural classification is a concept closely related to the concept natural kind.
Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...
is often recognized as the first scholar to clearly have differentiated "artificial" and "natural" classifications A natural classification is one, using Plato's metaphor, that is “carving nature at its joints” Although Linnaeus considered natural classification the ideal, he recognized that his own system (at least partly) represented an artificial classification. John Stuart Mill explained the artificial nature of the Linnaean classification and suggested the following definition of a natural classification:
"The Linnæan arrangement answers the purpose of making us think together of all those kinds of plants, which possess the same number of stamens and pistils; but to think of them in that manner is of little use, since we seldom have anything to affirm in common of the plants which have a given number of stamens and pistils.""The ends of scientific classification are best answered, when the objects are formed into groups respecting which a greater number of general propositions can be made, and those propositions more important, than could be made respecting any other groups into which the same things could be distributed." "A classification thus formed is properly scientific or philosophical, and is commonly called a Natural, in contradistinction to a Technical or Artificial, classification or arrangement."
Ridley (1986) provided the following definitions: * "artificial classification. The term (like its opposite, ''natural classification'') has many meanings; in this book I have picked a ''phenetic'' meaning. A classificatory group will be defined by certain characters, called ''defining characters''; in an artificial classification, the members of a group resemble one another in their defining characters (as they must, by definition) but not in their non-defining characters. With respect to the characters not used in the classification, the members of a group are uncorrelated. * "natural classification. Classificatory groups are defined by certain characters, called 'defining' characters; in a natural group, the members of the group resemble one another for non-defining characters as well as for the defining character. This is not the only meaning for what is perhaps the most variously used term in taxonomy ...


Taxonomic monism vs. pluralism

Stamos (2004) wrote: "The fact is, modern scientists classify atoms into elements based on proton number rather than anything else because it alone is the causally privileged factor old is atomic number 79 in the periodic table because it has 79 protons in its nucleus Thus nature itself has supplied the causal monistic essentialism. Scientists in their turn simply discover and follow (where "simply" ≠ "easily")."


Examples of important taxonomies


Periodic table

The
periodic table The periodic table, also known as the periodic table of the elements, is an ordered arrangement of the chemical elements into rows (" periods") and columns (" groups"). It is an icon of chemistry and is widely used in physics and other s ...
is the classification of the chemical elements which is in particular associated with
Dmitri Mendeleev Dmitri Ivanovich Mendeleev ( ; ) was a Russian chemist known for formulating the periodic law and creating a version of the periodic table of elements. He used the periodic law not only to correct the then-accepted properties of some known ele ...
(cf., History of the periodic table). An authoritative work on this system is Scerri (2020). Hubert Feger (2001; numbered listing added) wrote about it: "A well-known, still used, and expanding classification is Mendeleev's Table of Elements. It can be viewed as a prototype of all taxonomies in that it satisfies the following evaluative criteria: # Theoretical foundation: A theory determines the classes and their order. # Objectivity: The elements can be observed and classified by anybody familiar with the table of elements. # Completeness: All elements find a unique place in the system, and the system implies a list of all possible elements. # Simplicity: Only a small amount of information is used to establish the system and identify an object. # Predictions: The values of variables not used for classification can be predicted (number of electrons and atomic weight), as well as the existence of relations and of objects hitherto unobserved. Thus, the validity of the classification system itself becomes testable." Bursten (2020) wrote, however "Hepler-Smith, a historian of chemistry, and I, a philosopher whose work often draws on chemistry, found common ground in a shared frustration with our disciplines’ emphases on the chemical elements as the stereotypical example of a natural kind. The frustration we shared was that while the elements did display many hallmarks of paradigmatic kindhood, elements were not the kinds of kinds that generated interesting challenges for classification in chemistry, nor even were they the kinds of kinds that occupied much contemporary critical chemical thought. Compounds, complexes, reaction pathways, substrates, solutions – these were the kinds of the chemistry laboratory, and rarely if ever did they slot neatly into taxonomies in the orderly manner of classification suggested by the Periodic Table of Elements. A focus on the rational and historical basis of the development of the Periodic Table had made the received view of chemical classification appear far more pristine, and far less interesting, than either of us believed it to be."


Linnaean taxonomy

Linnaean taxonomy Linnaean taxonomy can mean either of two related concepts: # The particular form of biological classification (taxonomy) set up by Carl Linnaeus, as set forth in his ''Systema Naturae'' (1735) and subsequent works. In the taxonomy of Linnaeus th ...
is the particular form of biological classification (
taxonomy image:Hierarchical clustering diagram.png, 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme o ...
) set up by
Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...
, as set forth in his
Systema Naturae ' (originally in Latin written ' with the Orthographic ligature, ligature æ) is one of the major works of the Sweden, Swedish botanist, zoologist and physician Carl Linnaeus (1707–1778) and introduced the Linnaean taxonomy. Although the syste ...
(1735) and subsequent works. A major discussion in the scientific literature is whether a system that was constructed before Charles Darwin's theory of evolution can still be fruitful and reflect the development of life.


Astronomy

Astronomy Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...
is a fine example on how Kuhn's (1962) theory of scientific revolutions (or paradigm shifts) influences classification. For example: * Paradigm one: Ptolemaic astronomers might learn the concepts "star" and "planet" by having the Sun, the Moon, and Mars pointed out as instances of the concept “planet” and some fixed stars as instances of the concept “star.” * Paradigm two: Copernicans might learn the concepts "star", "planet", and "satellites" by having Mars and Jupiter pointed out as instances of the concept “planet,” the Moon as an instance of the concept “satellite,” and the Sun and some fixed stars as instances of the concept "star". Thus, the concepts "star", "planet", and "satellite" got a new meaning and astronomy got a new classification of celestial bodies.


Hornbostel–Sachs classification of musical instruments

Hornbostel–Sachs Hornbostel–Sachs or Sachs–Hornbostel is a system of musical instrument classification devised by Erich Moritz von Hornbostel and Curt Sachs, first published in the in 1914. An English translation was published in the '' Galpin Society Journ ...
is a system of musical instrument classification devised by Erich Moritz von Hornbostel and Curt Sachs, and first published in 1914. In the original classification, the top categories are: * Idiophones: instruments that rely on the body of the instrument to create and resonate sound. *
Membranophone A membranophone is any musical instrument which produces sound primarily by way of a acoustic membrane, vibrating stretched membrane. It is one of the four main divisions of instruments in the original Hornbostel-Sachs scheme of musical instrument ...
s: instruments that have a membrane that is stretched over a structure, often wood or metal, and struck or rubbed to produce a sound. The subcategories are largely determined by the shape of the structure that the membrane is stretched over. *
Chordophone In musical instrument classification, string instruments, or chordophones, are musical instruments that produce sound from vibrating strings when a performer strums, plucks, strikes or sounds the strings in varying manners. Musicians play some ...
: Instruments that use vibrating strings, which are most commonly stretched across a metal or wooden structure, to create sound. * Aerophones Instruments that require air passing through, or across, them to create sound. Most commonly constructed of wood or metal. A fifth top category, * Electrophones: Instruments that require electricity to be amplified and heard. This group was added by Sachs in 1940. Each top category is subdivided and Hornbostel-Sachs is a very comprehensive classification of musical instruments with wide applications. In Wikipedia, for example, all musical instruments are organized according to this classification. In opposition to, for example, the astronomical and biological classifications presented above, the Hornbostel-Sachs classification seems very little influenced by research in
musicology Musicology is the academic, research-based study of music, as opposed to musical composition or performance. Musicology research combines and intersects with many fields, including psychology, sociology, acoustics, neurology, natural sciences, ...
and
organology Organology (; ) is the science of musical instruments and their classifications. It embraces study of instruments' history, instruments used in different cultures, technical aspects of how instruments produce sound, and musical instrument classi ...
. It is based on huge collections of musical instruments, but seems rather as a system imposed upon the universe of instruments than as a system with organic connections to scholarly theory. It may therefore be interpreted as a system based on logical division and rationalist philosophy.


Diagnostic and Statistical Manual of Mental Disorders (DSM)

Diagnostic and Statistical Manual of Mental Disorders The ''Diagnostic and Statistical Manual of Mental Disorders'' (''DSM''; latest edition: ''DSM-5-TR'', published in March 2022) is a publication by the American Psychiatric Association (APA) for the classification of mental disorders using a com ...
(DSM) is a classification of mental disorders published by the American Psychiatric Association (APA).The first edition of the DSM was published in 1952, and the newest, fifth edition was published in 2013. In contrast to, for example, the periodic table and the Hornbostel-Sachs classification, its principles for classification have changed much during its history. The first edition was influenced by psychodynamic theory. The DSM-III, published in 1980, adopted an atheoretical, “descriptive” approach to classification The system is very important for all people involved in psychiatry, whether as patients, researchers or therapists (in addition to insurance companies), but it is also strongly criticized and does not have the same scientific status as many other classifications.Cooper, Rachel. 2017. “Diagnostic and Statistical Manual of Mental Disorders (DSM)”. ''Knowledge Organization'' 44, no. 8: 668-76.


Sample list of taxonomies


Business, organizations, and economics

* Classification of customers, for marketing (as in
Master data management Master data management (MDM) is a discipline in which business and information technology collaborate to ensure the uniformity, accuracy, stewardship, semantic consistency, and accountability of the enterprise's official shared master data assets. ...
) or for profitability (e.g. by Activity-based costing) *
Classified information Classified information is confidential material that a government deems to be sensitive information which must be protected from unauthorized disclosure that requires special handling and dissemination controls. Access is restricted by law or ...
, as in legal or government documentation * Job classification, as in job analysis * Standard Industrial Classification, economic activities


Mathematics

* Attribute-value system, a basic knowledge representation framework * Classification theorems in mathematics * Mathematical classification, grouping mathematical objects based on a property that all those objects share *
Statistical classification When classification is performed by a computer, statistical methods are normally used to develop the algorithm. Often, the individual observations are analyzed into a set of quantifiable properties, known variously as explanatory variables or ''f ...
, identifying to which of a set of categories a new observation belongs, on the basis of a training set of data


Media

*
Classification (literature) Classification is a figure of speech linking a proper noun to a common noun using ''the'' or other articles.Robert E. Owens, "Language Development", 7th Edition, Content Technologies (2012). Example * "Finland, the land of a thousand lakes." * ...
, a figure of speech linking a proper noun to a common noun using ''the'' or other articles * Decimal classification, decimal classification systems *
Document classification Document classification or document categorization is a problem in library science, information science and computer science. The task is to assign a document to one or more Class (philosophy), classes or Categorization, categories. This may be do ...
, a problem in library science, information science and computer science **
Classified information Classified information is confidential material that a government deems to be sensitive information which must be protected from unauthorized disclosure that requires special handling and dissemination controls. Access is restricted by law or ...
, sensitive information to which access is restricted by law or regulation to particular classes of people **
Library classification A library classification is a system used within a library to organize materials, including books, sound and video recordings, electronic materials, etc., both on shelves and in catalogs and indexes. Each item is typically assigned a call number ...
, a system of coding, assorting and organizing library materials according to their subject * Image classification in computer vision *
Motion picture rating system A motion picture content rating system classifies films based on their suitability for audiences due to their treatment of issues such as sex, violence, or substance abuse, their use of profanity, or other matters typically deemed unsuitable for ...
, for film classification


Science

* Scientific classification (disambiguation) **
Biological classification In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon), and these groups are give ...
of organisms ** Chemical classification **
Medical classification A medical classification is used to transform descriptions of medical diagnoses or procedures into standardized statistical code in a process known as clinical coding. Diagnosis classifications list diagnosis codes, which are used to track dise ...
, the process of transforming descriptions of medical diagnoses and procedures into universal medical code numbers **
Taxonomic classification In biology, taxonomy () is the scientific study of naming, defining ( circumscribing) and classifying groups of biological organisms based on shared characteristics. Organisms are grouped into taxa (singular: taxon), and these groups are given ...
, also known as classification of species ***
Cladistics Cladistics ( ; from Ancient Greek 'branch') is an approach to Taxonomy (biology), biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesiz ...
, an approach using similarities


Other

* An industrial process such as
mechanical screening Mechanical screening, often just called screening, is the practice of taking granulated or crushed ore material and separating it into multiple grades by particle size. This practice occurs in a variety of industries such as mining and minera ...
for sorting materials by size, shape, density, etc. *
Civil service The civil service is a collective term for a sector of government composed mainly of career civil service personnel hired rather than elected, whose institutional tenure typically survives transitions of political leadership. A civil service offic ...
classification, personnel grades in government * Classification of swords *
Classification of wine The classification of wine is based on various criteria including Protected designation of origin, place of origin or appellation, vinification method and style, Sweetness of wine, sweetness and vintage,J. Robinson (ed) ''"The Oxford Companion to W ...
* Locomotive classification * Product classification * Security classification, information to which access is restricted by law or regulation * Ship classification society, a non-governmental organization that establishes and maintains technical standards for the construction and operation of ships and offshore structures


Organizations involved in taxonomy

* International Society for Knowledge Organization *
Classification Society A ship classification society or ship classification organisation is a non-governmental organization that establishes and maintains technical standards for the construction and operation of Shipping, ships and Offshore platform, offshore structure ...
.


See also

* * * *
Categorization Classification is the activity of assigning objects to some pre-existing classes or categories. This is distinct from the task of establishing the classes themselves (for example through cluster analysis). Examples include diagnostic tests, identi ...
, the process of dividing things into groups *
Classification (general theory) Classification is the activity of assigning objects to some pre-existing classes or categories. This is distinct from the task of establishing the classes themselves (for example through cluster analysis). Examples include diagnostic tests, identif ...
* Celestial Emporium of Benevolent Recognition, a fictional Chinese encyclopedia with an "impossible" taxonomic scheme *
Conflation Conflation is the merging of two or more sets of information, texts, ideas, or opinions into one, often in error. Conflation is defined as 'fusing blending', but is often used colloquially as 'being equal to' - treating two similar but disparate c ...
* Faceted classification *
Folksonomy Folksonomy is a classification system in which end users apply public tags to online items, typically to make those items easier for themselves or others to find later. Over time, this can give rise to a classification system based on those tag ...
* Gellish English dictionary, a taxonomy in which the concepts are arranged as a subtype–supertype hierarchy *
Hypernym Hypernymy and hyponymy are the semantic relations between a generic term (''hypernym'') and a more specific term (''hyponym''). The hypernym is also called a ''supertype'', ''umbrella term'', or ''blanket term''. The hyponym names a subtype of ...
*
Knowledge representation Knowledge representation (KR) aims to model information in a structured manner to formally represent it as knowledge in knowledge-based systems whereas knowledge representation and reasoning (KRR, KR&R, or KR²) also aims to understand, reason, and ...
*
Lexicon A lexicon (plural: lexicons, rarely lexica) is the vocabulary of a language or branch of knowledge (such as nautical or medical). In linguistics, a lexicon is a language's inventory of lexemes. The word ''lexicon'' derives from Greek word () ...
*
Ontology (information science) In information science, an ontology encompasses a representation, formal naming, and definitions of the categories, properties, and relations between the concepts, data, or entities that pertain to one, many, or all domains of discourse. More ...
, formal representation of knowledge as a set of concepts within a domain * Philosophical language * Protégé (software) * Semantic network * Semantic similarity network *
Structuralism Structuralism is an intellectual current and methodological approach, primarily in the social sciences, that interprets elements of human culture by way of their relationship to a broader system. It works to uncover the structural patterns t ...
*
Systematics Systematics is the study of the diversification of living forms, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees (synonyms: phylogenetic trees, phylogenies). Phy ...
*
Taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...
, a population of organisms that a taxonomist adjudges to be a unit *
Taxonomy for search engines Taxonomy for search engines refers to classification methods that improve relevance in vertical search. Taxonomies of entities are tree structures whose nodes are labelled with entities likely to occur in a web search query. Searches use these tre ...
* Thesaurus (information retrieval) * Typology (disambiguation)


Notes


References

* Atran, S. (1993) ''Cognitive Foundations of Natural History: Towards an Anthropology of Science.'' Cambridge:
Cambridge University Press Cambridge University Press was the university press of the University of Cambridge. Granted a letters patent by King Henry VIII in 1534, it was the oldest university press in the world. Cambridge University Press merged with Cambridge Assessme ...
. * Carbonell, J. G. and J. Siekmann, eds. (2005)
''Computational Logic in Multi-Agent Systems,'' Vol. 3487.
Berlin:
Springer-Verlag Springer Science+Business Media, commonly known as Springer, is a German multinational publishing company of books, e-books and peer-reviewed journals in science, humanities, technical and medical (STM) publishing. Originally founded in 1842 in ...
. * Malone, Joseph L. (1988)
''The Science of Linguistics in the Art of Translation: Some Tools from Linguistics for the Analysis and Practice of Translation.''
Albany, New York:
State University of New York Press The State University of New York Press (more commonly referred to as the SUNY Press) is a university press affiliated with the State University of New York system. The press, which was founded in 1966, is located in Albany, New York and publishe ...
.
OCLC 15856738
* *Marcello Sorce Keller, "The Problem of Classification in Folksong Research: a Short History", ''Folklore'', XCV(1984), no. 1, 100–104. * Chester D Rowe and Stephen M Davis, 'The Excellence Engine Tool Kit'; * *


External links

* * *
Taxonomy 101: The Basics and Getting Started with Taxonomies
'
Parrochia, Daniel 2016. "Classification"
In ''The Internet Encyclopedia of Philosophy'' eds. James Fieser and Bradley Dowden. {{Authority control Scientific nomenclature Hierarchy Ontology Types of groupings