The sorting inspection method refers to the organization method that a certain number of files or other information records or file entities are sorted according to certain marks and rules, and checked according to the same marks and rules. Classification methods are widely used, such as the compilation of retrieval tools and retrieval systems, the compilation of reference books, the shelving of documents, the compilation of telephone books, codebooks and character sets, and the compilation of various lists. The commonly used sorting methods are sorting, word sorting, number sorting, time sequencing and ground sequencing. Derived indexing method is a method of selecting and compiling thematic directories and indexes by using existing directories and indexes.