资料来源 : pyDict

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资料来源 : Webster's Revised Unabridged Dictionary (1913)

Redundance \Re*dun"dance\ (r?*d?n"dans), Redundancy
\Re*dun"dan*cy\ (-dan*s?), n. [L. redundantia: cf. F.
   redondance.]
   1. The quality or state of being redundant; superfluity;
      superabundance; excess.

   2. That which is redundant or in excess; anything superfluous
      or superabundant.

            Labor . . . throws off redundacies.   --Addison.

   3. (Law) Surplusage inserted in a pleading which may be
      rejected by the court without impairing the validity of
      what remains.

资料来源 : WordNet®

redundancy
     n 1: repetition of messages to reduce the probability of errors
          in transmission
     2: the attribute of being superfluous and unneeded; "the use of
        industrial robots created redundancy among workers" [syn:
        {redundance}]
     3: (electronics) a system design that duplicates components to
        provide alternatives in case one component fails
     4: repetition of an act needlessly

资料来源 : Free On-Line Dictionary of Computing

redundancy
     
        1.  The provision of multiple interchangeable
        components to perform a single function in order to cope with
        failures and errors.  Redundancy normally applies primarily to
        hardware.  For example, one might install two or even three
        computers to do the same job.  There are several ways these
        could be used.  They could all be active all the time thus
        giving extra performance through {parallel processing} as well
        as extra availability; one could be active and the others
        simply monitoring its activity so as to be ready to take over
        if it failed ("warm standby"); the "spares" could be kept
        turned off and only switched on when needed ("cold standby").
        Another common form of hardware redundancy is {disk
        mirroring}.
     
        Redundancy can also be used to detect and recover from errors,
        either in hardware or software.  A well known example of this
        is the {cyclic redundancy check} which adds redundant data to
        a block in order to detect corruption during storage or
        transmission.  If the cost of errors is high enough, e.g. in a
        {safety-critical system}, redundancy may be used in both
        hardware AND software with three separate computers programmed
        by three separate teams and some system to check that they all
        produce the same answer, or some kind of majority voting
        system.
     
        2.  The proportion of a message's gross
        information content that can be eliminated without losing
        essential information.
     
        Technically, redundancy is one minus the ratio of the actual
        uncertainty to the maximum uncertainty.  This is the fraction
        of the structure of the message which is determined not by the
        choice of the sender, but rather by the accepted statistical
        rules governing the choice of the symbols in question.
     
        [Shannon and Weaver, 1948, p. l3]
     
        [Better explanation?]
     
        (1995-05-09)