Figure 2.

Two interacting proteins, P₁ and P₂, with their respective annotation terms. An annotation link is created by linking an annotation from the first protein's annotation set to another annotation of the second protein. Above, the tuples {(a₁, a₂), (a₁, a₄), (a₂, a₂), (a₂, a₄), (a₃, a₂), (a₃, a₄)} are shown. There are a total of 3 × 2 = 6 annotation links between P₁ and P₂.