The origin of four-part classification

Then in the Western Han Dynasty, Liu Xiang and his son compiled Seven Laws, which were divided into seven parts: Seven Laws, Six Artistic Laws, Zhuzi Law, Poetry Law, Military Law, Shu Shu Law and Ji Fang Law, among which the Seven Laws was actually a general preface, so it could be temporarily called Liu Fenfa. However, the literature of literature and history, Buddhist scriptures, Yin-Yang writers and Five Elements writers has increased, and this classification method can no longer meet the classification needs. During the reign of Emperor Wu of Jin Dynasty, the secretary supervisor Xun Xu and the secretariat Zhang Hua sorted out books and collected bamboo books, so they copied Wei Zhongjing's thin book and compiled it into a new thin book of Zhongjing. This classification changed the original system, and the book was divided into four parts: A, B, C and D. In the Annals of Classics and Records of Sui Shu compiled by officials in the early Tang Dynasty, it was named and classified by four subsets of classics and history for the first time, which formally established the position of quartering in ancient bibliography. Finally, when the Qing Dynasty edited Sikuquanshu, the largest series in ancient China, it divided the abstracts of ancient books written in the editing process into four parts according to the subsets of classics and history, and compiled it into the Summary of Sikuquanshu. This is the establishment of the classification of classical and historical subsets.