2. The International Organization for Standardization (ISO) stipulates that each member country should print UDC classification number on the cover of its national standard to facilitate international communication and information exchange.
3. The International Decimal Classification was put forward and compiled by Belgian Otto Qin and Tifontein in 1985. Its purpose is to classify monographs and papers on social politics, science and technology and culture.
4. Because UDC has the characteristics of multi-language, multi-version, detailed classification, flexible combination and strong indexing ability, it can not only be applied to the classification and shelving of books, but also meet the classification requirements of individual documents. It is not only suitable for manual retrieval, but also successfully applied to machine retrieval, thus becoming one of the international information retrieval languages.
5. After the publication of UCD, it was supported and adopted by many countries. It is called the international communication language in the field of library and information, and occupies an important position in many classifications in the world.
6. Some ideas and viewpoints of 6.UCD represent the development direction of book classification, which is a good reference for us to compile and revise book classification.