Information is an abstract concept that refers to something which has the power to inform. At the most fundamental level, it pertains to the interpretation (perhaps formally) of that which may be sensed, or their abstractions. Any natural process that is not completely random and any observable pattern in any medium can be said to convey some amount of information. Whereas digital signals and other data use discrete signs to convey information, other phenomena and artifacts such as analogue signals, poems, pictures, music or other sounds, and currents convey information in a more continuous form. Information is not knowledge itself, but the meaning that may be derived from a representation through interpretation.
The concept of information is relevant to and connected with various concepts, including constraint, communication, control, data, form, education, knowledge, meaning, understanding, mental stimuli, pattern, perception, proposition, representation, and entropy.
Information is often processed iteratively: Data available at one step are processed into information to be interpreted and processed at the next step. For example, in written text each symbol or letter conveys information relevant to the word it is part of, each word conveys information relevant to the phrase it is part of, each phrase conveys information relevant to the sentence it is part of, and so on until at the final step information is interpreted and becomes knowledge in a given domain. In a digital signal, bits may be interpreted into the symbols, letters, numbers, or structures that convey the information available at the next level up. The key characteristic of information is that it is subject to interpretation and processing.
The derivation of information from a signal or message may be thought of as the resolution of ambiguity or uncertainty that arises during the interpretation of patterns within the signal or message.
Information may be structured as data. Redundant data can be compressed up to an optimal size, which is the theoretical limit of compression.
The information available through a collection of data may be derived by analysis. For example, a restaurant collects data from every customer order. That information may be analyzed to produce knowledge that is put to use when the business subsequently wants to identify the most popular or least popular dish.
Information can be transmitted in time, via data storage, and space, via communication and telecommunication. Information is expressed either as the content of a message or through direct or indirect observation. That which is perceived can be construed as a message in its own right, and in that sense, all information is always conveyed as the content of a message.
Information can be encoded into various forms for transmission and interpretation (for example, information may be encoded into a sequence of signs, or transmitted via a signal). It can also be encrypted for safe storage and communication.
The uncertainty of an event is measured by its probability of occurrence. Uncertainty is proportional to the negative logarithm of the probability of occurrence. Information theory takes advantage of this by concluding that more uncertain events require more information to resolve their uncertainty. The bit is the standard unit of information. It is 'that which reduces uncertainty by half'. Other units such as the nat may be used. For example, the information encoded in one "fair" coin flip is log2(2/1) = 1 bit, and in two fair coin flips is log2(4/1) = 2 bits. A 2011 Science article estimates that 97% of technologically stored information was already in digital bits in 2007 and that the year 2002 was the beginning of the digital age for information storage (with digital storage capacity bypassing analogue for the first time). Free access to the article at martinhilbert.net/WorldInfoCapacity.html
Etymology and history of the concept
The English word "information" comes from Middle French enformacion/informacion/information 'a criminal investigation' and its etymon, Latin informatiō(n) 'conception, teaching, creation'.Oxford English Dictionary, Third Edition, 2009, full text
In English, "information" is an uncountable mass noun.
References on "formation or molding of the mind or character, training, instruction, teaching" date from the 14th century in both English (according to Oxford English Dictionary) and other European languages. In the transition from Middle Ages to Modernity the use of the concept of information reflected a fundamental turn in epistemological basis – from "giving a (substantial) form to matter" to "communicating something to someone". Peters (1988, pp. 12–13) concludes:
Information was readily deployed in empiricist psychology (though it played a less important role than other words such as impression or idea) because it seemed to describe the mechanics of sensation: objects in the world inform the senses. But sensation is entirely different from "form" – the one is sensual, the other intellectual; the one is subjective, the other objective. My sensation of things is fleeting, elusive, and idiosyncratic. For Hume, especially, sensory experience is a swirl of impressions cut off from any sure link to the real world... In any case, the empiricist problematic was how the mind is informed by sensations of the world. At first informed meant shaped by; later it came to mean received reports from. As its site of action drifted from cosmos to consciousness, the term's sense shifted from unities (Aristotle's forms) to units (of sensation). Information came less and less to refer to internal ordering or formation, since empiricism allowed for no preexisting intellectual forms outside of sensation itself. Instead, information came to refer to the fragmentary, fluctuating, haphazard stuff of sense. Information, like the early modern worldview in general, shifted from a divinely ordered cosmos to a system governed by the motion of corpuscles. Under the tutelage of empiricism, information gradually moved from structure to stuff, from form to substance, from intellectual order to sensory impulses.Peters, J. D. (1988). Information: Notes Toward a Critical History. Journal of Communication Inquiry, 12, 10-24.
In the modern era, the most important influence on the concept of information is derived from the Information theory developed by Claude Shannon and others. This theory, however, reflects a fundamental contradiction. Northrup (1993)Qvortrup, L. (1993). The controversy over the concept of information. An overview and a selected and annotated bibliography. Cybernetics & Human Knowing 1(4), 3-24. wrote:
Thus, actually two conflicting metaphors are being used: The well-known metaphor of information as a quantity, like water in the water-pipe, is at work, but so is a second metaphor, that of information as a choice, a choice made by :an information provider, and a forced choice made by an :information receiver. Actually, the second metaphor implies that the information sent isn't necessarily equal to the information received, because any choice implies a comparison with a list of possibilities, i.e., a list of possible meanings. Here, meaning is involved, thus spoiling the idea of information as a pure "Ding an sich." Thus, much of the confusion regarding the concept of information seems to be related to the basic confusion of metaphors in Shannon's theory: is information an autonomous quantity, or is information always per SE information to an observer? Actually, I don't think that Shannon himself chose one of the two definitions. Logically speaking, his theory implied information as a subjective phenomenon. But this had so wide-ranging epistemological impacts that Shannon didn't seem to fully realize this logical fact. Consequently, he continued to use metaphors about information as if it were an objective substance. This is the basic, inherent contradiction in Shannon's information theory." (Northrup, 1993, p. 5).
In their seminal book The Study of Information: Interdisciplinary Messages,Machlup, Fritz & Una Mansfield (eds.). 1983. The Study of Information: Interdisciplinary Messages. New York: Wiley. Almach and Mansfield (1983) collected key views on the interdisciplinary controversy in computer science, artificial intelligence, library and information science, linguistics, psychology, and physics, as well as in the social sciences. Almach (1983,Machlup, Fritz. 1983. "Semantic Quirks in Studies of Information," pp. 641-71 in Fritz Machlup & Una Mansfield, The Study of Information: Interdisciplinary Messages. New York: Wiley. p. 660) himself disagrees with the use of the concept of information in the context of signal transmission, the basic senses of information in his view all referring "to telling something or to the something that is being told. Information is addressed to human minds and is received by human minds." All other senses, including its use with regard to nonhuman organisms as well to society as a whole, are, according to Machlup, metaphoric and, as in the case of cybernetics, anthropomorphic.
Hjørland (2007)Hjørland, B. (2007). Information: Objective or Subjective/Situational?. Journal of the American Society for Information Science and Technology, 58(10), 1448-1456. describes the fundamental difference between objective and subjective views of information and argues that the subjective view has been supported by, among others, Bateson,Bateson, G. (1972). Steps to an ecology of mind. New York: Ballantine. Yovits,Yovits, M.C. (1969). Information science: Toward the development of a true scientific discipline. American Documentation (Vol. 20, pp. 369–376).Yovits, M. C. (1975). A theoretical framework for the development of information science. In International Federation for Documentation. Study Committee Research on the Theoretical Basis of Information. Meeting (1974: Moscow) Information science, its scope, objects of research and problems: Collection of papers [presented at the meeting of the FID Study Committee "Research on the Theoretical Basis of Information"] 24–26 April 1974, Moscow (pp. 90–114). FID 530. Moscow: VINITI Span-Hansen,Spang-Hanssen, H. (2001). How to teach about information as related to documentation. Human IT, (1), 125–143. Retrieved May 14, 2007, from http://www.hb.se/bhs/ith/1-01/hsh.htm Brier,Brier, S. (1996). Cybersemiotics: A new interdisciplinary development applied to the problems of knowledge organisation and document retrieval in information science. Journal of Documentation, 52(3), 296–344. Buckland,Buckland, M. (1991). Information and information systems. New York: Greenwood Press. Goguen,Goguen, J. A. (1997). Towards a social, ethical theory of information. In G. Bowker, L. Gasser, L. Star, & W. Turner, Erlbaum (Eds.), Social science research, technical systems and cooperative work: Beyond the great divide (pp. 27–56). Hillsdale, NJ: Erlbaum. Retrieved May 14, 2007, from http://cseweb.ucsd.edu/~goguen/ps/sti.pdf and Hjørland.Hjørland, B. (1997). Information seeking and subject representation. An activity-theoretical approach to information science. Westport: Greenwood Press. Hjørland provided the following example: