2.3. Sets
A set is any collection of objects, called its elements. Normally the elements have the same type (e.g., integers or animals), in which case the set is said to be typed. The set of all elements of that type is called the universe of discourse, often symbolised by U. (Sets of elements of mixed types are often referred to as collections.)
2.3.1. Set Notation
A set of three males may be written as 
. The members of a set have no order, so 
is the same set. Nor does it matter if elements are duplicated, so
. The members of a set have no order, so is the same set. Nor does it matter if elements are duplicated, so Get Systems Analysis and Synthesis now with the O’Reilly learning platform.
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