Figure 1.

Example atom mappings. Example reaction r: m₁ → m₂ + m₃, two alternative atom mappings Γ₁(r) = {(a₁, a₃), (a₂, a₄)} (left) and Γ₂(r) = {(a₁, a₄), (a₂, a₃)} (right) and corresponding atom graphs G({r}) for atom mappings Γ₁, Γ₂. Atom mappings indicated by shading of atoms. The reaction consumes atoms (r) = {a₁, a₂} and produces atoms (r) = {a₃, a₄}.