Document sorting, that is, document classification, refers to the systematic organization and differentiation of documents according to different directions of their contents and forms and a certain system. In order to facilitate literature retrieval, literature classification methods must be scientific and reasonable. Literature classification is a classification system organized by many categories according to certain principles, and the categories at all levels are represented by tags and their order is fixed.

Literature classification includes: Chinese library book classification, China book data classification, China Academy of Sciences library book classification, Renmin University of China library book classification, international book integration classification, etc. With the in-depth study of literature classification theory, the original classification is becoming more and more perfect, and new classification is also emerging.

The traditional enumeration classification method for expanding data is gradually developing to faceted combination classification method. Including: continue to improve the classification of facet combination, so as to achieve the purpose of practical application; Transform the traditional enumeration classification to make it gradually develop into noodle formula; Enumeration taxonomy is used in combination with faceted combination taxonomy.

Classification and subject method gradually tend to merge. Classification and subject method are increasingly compatible in concept (terminology) system, reference system, indexing system, indexing system and retrieval system. Literature classification tends to standardization and internationalization. ⑤ The compilation, management, indexing and retrieval of document classification tables are becoming more and more automatic.

Baidu Encyclopedia-Literature Classification