Incidence Structure - Dual Structure

Dual Structure

If we interchange the role of "points" and "lines" in

C=(P,L,I)

the dual structure

C*=(L,P,I*)

is obtained, where I* is the inverse relation of I. Clearly

C**=C.

This is an abstract version of projective duality.

A structure C that is isomorphic to its dual C* is called self-dual.

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