Redundancy, in general usage, means more than enough. What is enough depends very much on a number of circumstances and criteria. If we are concerned with information, such factors as the reliability of components, the importance of the level of accuracy of a message or the requirement for timely action in a diversified command situation, are needed to make appropriate decisions. If we are concerned instead with, the distribution of food, the rate of spoilage over given distances at different (???) the margins in our temperature conditions will be a key factor. In management, the use of a redundant network of committees, contacts in the field, social groupings and trade publications provides a **hedge against error** which is sometimes not given full recognition. The human brain operates on components which are **redundant by a factor in the tens of thousands**.
Several specific aspects of redundancy are of particular interest: in the information theory propounded by Shannon and Weaver, (p. 104) the redundancy is "the fraction of the structure of the message which is determined not by the free choice of the sender, but rather by the accepted statistical rules governing the use of the symbols in question." The English language is about fifty percent redundant, which makes it a good language for crossword puzzles. This usage of redundancy may be expressed mathematically as "one minus the relative entropy”.
In the 'redundancy of potential command' described by Warren McCullough (p. 226) "knowledge constitutes authority”. He described a naval battle in which each ship peers through the smoke and fog for evidence of the enemy's activity and relays that information to the others. The command passes from one ship with incomplete information to another according to who has the best information at that time. Victory was attributed to the early loss of the central command ship which eliminated the traditional command hierarchy.
# SOURCE The word itself comes from the Latin 'redundans' meaning overflowing. In addition to Shannon, Weaver, the mathematician John Von Neumann made significant early contributions-to the understanding of redundancy in information networks. McCulloch, W. (1965). *Embodiments of Mind*. Cambridge MA: MIT Press.
# EXAMPLES • the additional portion of a message which enables it to be understood by the receiver even if part of the message is lost or obliterated by noise • the additional number of channels or media required to get a message to an especially important receiver (such as in espionage) • a critical proportion of dispersed receivers (such as are required if a marketing campaign is to work) • the amount of backlog (described by queuing theory required to gain the most efficient use of a machine or an input channel
# NON-EXAMPLES • the creation of a management decision structure where a single unit decides for itself on a preset allocation of responsibility without consulting others • sending an important message by a single route which may entirely fail (such as a letter) or introduce distortion (such as a corrupt messenger) • building a building which needs ventilation with windows that don't open • the absence of manual controls if automatic ones fail
# PROBABLE ERROR • Not allowing for necessary redundancy by looking at it as a constant (such as a **cost cutting target**) rather than as a variable to be adjusted • Not realizing the **vulnerability of a system** • Relying on a charismatic individual to advance a cause with no provision for **succession** • Idiosyncratic information paths • Historical dependence • Unrepeatable circumstances
# SEE Information; Entropy; Channel capacity; Self-organization; Noise
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Massive redundancy has been discovered within string representations, due not only to accidental structure supported by the linear medium but also due to irrelevant structure embedded within the string representation of concepts and operations. pdf 
(p. 382–383)