Mapping is an important concept in relating the elements or subsets of one universal set to elements or sets in another universe of discourse. If X and Y are two different universal sets, and if element x is contained in ‘X’ corresponds to an element 1 contained in ‘Y’ then it is generally termed as a mapping from X to Y or as f : X -> Y
When A ={x, y, z}, mapping the characteristic function membership of elements is denoted by χA and is defined as: Membership of element x in set A χA = 1, x ∈ A
where x represents an element in set A.