  This paper presents a canonical d.c. (difference of canonical and convex
functions) programming problem, which can be used to model general global
optimization problems in complex systems. It shows that by using the canonical
duality theory, a large class of nonconvex minimization problems can be
equivalently converted to a unified concave maximization problem over a convex
domain, which can be solved easily under certain conditions. Additionally, a
detailed proof for triality theory is provided, which can be used to identify
local extremal solutions. Applications are illustrated and open problems are
presented.
