According to the processing depth of documents, they are divided into zero-level documents, first-level documents, second-level documents and third-level documents.

According to the carrier form of literature, it can be divided into printing type, miniature type, machine-readable type and digital type (CD-ROM type and online network type).

According to the publication form of documents, they are divided into books (monographs, reference books, teaching materials, historical books, ancient books, etc.). ), continuous publications (periodicals, newspapers, magazines) and special documents (patent documents, conference documents, standard documents, scientific and technological reports, government publications, product samples, etc. ).

Literary elements:

Literature consists of three elements, knowledge, carrier and recording method are inseparable. According to the definition of literature, this special carrier of literature must meet three basic conditions at the same time: first, it must have certain information and knowledge content, second, it must use certain recording means, and third, it must show certain carrier forms.

Information and knowledge are the main body of literature. Without information and knowledge, any form of carrier can only be called material, not literature. Any form and type of literature must first have certain information and knowledge content as the premise.