Figure 3. Coproduct: The coproduct (direct sum) is the dual to the product. It is defined by reversing all arrows in Figure 1. If S;M1;M2 are objects of the category C, then S is the coproduct of M1 and M2 if we can find an object X and morphisms i1 : M1 ! S, i2 : M2 ! S, c : M1 ! X, and f : M2 ! X such that there is a unique morphism u : S ! X.
...read more