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"Don't repeat yourself" (DRY), also known as "duplication is evil", is a principle of software development aimed at reducing repetition of information which is likely to change, replacing it with abstractions that are less likely to change, or using data normalization which avoids redundancy in the first place.
Sometimes the approaches suggest opposite solutions. For example, if a building catches fire, fail-safe systems would unlock doors to ensure quick escape and allow firefighters inside, while fail-secure would lock doors to prevent unauthorized access to the building. The opposite of fail-closed is called fail-open.
In engineering and systems theory, redundancy is the intentional duplication of critical components or functions of a system with the goal of increasing reliability of the system, usually in the form of a backup or fail-safe, or to improve actual system performance, such as in the case of GNSS receivers, or multi-threaded computer processing.
The idea of incorporating redundancy in order to improve the reliability of a system was pioneered by John von Neumann in the 1950s. [24] Two kinds of redundancy are possible: [25] space redundancy and time redundancy. Space redundancy provides additional components, functions, or data items that are unnecessary for fault-free operation.
A limited amount of redundancy can improve the effectiveness of communication, either for the whole readership or at least to offer help to those readers who need it. A phonetic example of that principle is the need for spelling alphabets in radiotelephony. Some instances of RAS syndrome can be viewed as syntactic examples of the principle.
In a high-availability server cluster, each individual server may attain internal component redundancy by having multiple power supplies, hard drives, and other components. System-level redundancy could be obtained by having spare servers waiting to take on the work of another server if it fails.
Linguists usually call this redundancy to avoid confusion with syntactic pleonasm, a more important phenomenon for theoretical linguistics. It usually takes one of two forms: Overlap or prolixity. Overlap: One word's semantic component is subsumed by the other: "Receive a free gift with every purchase."; a gift is usually already free.
Data integrity is the opposite of data corruption. [4] The overall intent of any data integrity technique is the same: ensure data is recorded exactly as intended (such as a database correctly rejecting mutually exclusive possibilities). Moreover, upon later retrieval, ensure the data is the same as when it was originally recorded. In short ...