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Definition: relation

R is a relation between S0, ..., Sn-1 : <=>
   R subset S0 x ... x Sn-1.
R is an n-ary relation : <=>
   exists S_0, ..., S_n-1: R  is a relation between  S_0, ..., S_n-1;
R is an n-ary relation on S : <=>
   R subset S x ... x S (cartesian product of n instances of S).
R is a relation on S : <=> R is a 2-ary ( binary) relation on S.

Set of tuples of related values.

Author: Wolfgang Schreiner
Last Modification: October 14, 1999

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