Since the food custom and recipes introduced from Tang (China) is supposed to have been assimilated and taken root in Japan in the ninth century, the custom and recipes may have been integrated into Yusoku-kojitsu (knowledge of court rules, ceremony, documents and records of the past) by Yamakage.
9世紀の段階で、唐から伝えられた食習慣・調理法が日本風に消化されて定着しつつあったと思われ、それらをまとめて有職故実という形で山蔭が結実させたものであろう。