Under the Ritsuryo system (a system of centralized government based on the ritsuryo code), a professor of the Daigaku-ryo (Bureau of Education under the ritsuryo system) or an individual with similar education and experience was appointed to the position of Jidoku.
律令制のもとでは大学寮の博士あるいはこれに近い学識を有する人物が任命された。