these properties assume the existence of at least two sets: a given universal set, denoted u, and the empty set, denoted {}. the algebra of sets describes the properties of all possible subsets of u, called the power set of u and denoted "p"(u). "p"(u) is assumed closed under union, intersection, and set complement. the algebra of sets is an interpretation or model of boolean algebra, with union, intersection, set complement, u, and {} interpreting boolean sum, product, complement, 1, and 0, respectively.