MAPPING
Definition
An object is <MAPPING> if and only if: it is a <STRUCTURE(math)>; it contains: a class or structure, called the 'domain'; a class or structure, called the 'range'; the <PRINCIPAL SET> consists of pairs (x, y), where x is a member of the domain and y is a member of the range. The <PRINCIPAL SET> set of a mapping is called the 'graph of mapping' or 'extension'