According to the so-called revelation principle, it is enough to study only a subset (the green triangle) of all mechanisms, the incentive-compatible direct mechanisms. These require each of the participants to disclose their private information and are structured so that it is optimal for each participant to report truthfully: to put their cards on the table. The subset of direct mechanisms is well-structured enough to enable mathematical analysis. This principle hence makes it possible to make general calculations for complicated decision-making processes where previously we have virtually had to resort to “trial and error”.