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Complete Product


A complete product for a finite family {A_k}_(k=1)^p of subsets of a fixed universal set U is an intersection of the form

 B_1B_2...B_p=B_1 intersection B_2 intersection ... intersection B_p,
(1)

where p is a nonnegative integer and each B_k is either A_k or its complement A^__k=U\A_k. There are 2^p formal choices, some of which may give the empty set. For p=0, the single complete product is U. For example, the 2^3=8 formal complete products of A={A_1,A_2,A_3} are

 A_1A_2A_3,A_1A_2A^__3,A_1A^__2A_3,A^__1A_2A_3,
 A_1A^__2A^__3,A^__1A_2A^__3,A^__1A^__2A_3,A^__1A^__2A^__3.
(2)

The nonempty complete products are pairwise disjoint and partition U. Each element of the generated Boolean algebra has a unique representation, up to order, as a union of these nonempty complete products, with the empty set represented by the empty union. In the following example, + denotes symmetric difference, which agrees with union for disjoint complete products:

A_1A_2 union A^__3=(A_1A_2A_3 union A_1A_2A^__3) union (A_1A_2A^__3 union A^__1A_2A^__3 union A_1A^__2A^__3 union A^__1A^__2A^__3)
(3)
=A_1A_2A_3 union A_1A_2A^__3 union A^__1A_2A^__3 union A_1A^__2A^__3 union A^__1A^__2A^__3
(4)
=A_1A_2A_3+A_1A_2A^__3+A^__1A_2A^__3+A_1A^__2A^__3+A^__1A^__2A^__3
(5)

(Comtet 1974, p. 186).


See also

Boolean Function, Conjunction

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References

Comtet, L. Advanced Combinatorics: The Art of Finite and Infinite Expansions, rev. enl. ed. Dordrecht, Netherlands: Reidel, p. 186, 1974.

Referenced on Wolfram|Alpha

Complete Product

Cite this as:

Weisstein, Eric W. "Complete Product." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/CompleteProduct.html

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