Information expansion: The International Patent Classification Table (IPC Classification) is compiled according to the Strasbourg Agreement on International Patent Classification signed in 197 1. It is the only international patent document classification and retrieval tool, and it is necessary for all countries in the world. The eighth edition of IPC has about 20,000 articles, including departments, major categories, minor categories, major groups and a few groups in some technical fields. There are about 70,000 articles in the advanced version of the eighth edition of IPC, including the basic edition and the items further subdivided in the basic edition. Advanced version is used by industrial property offices and large industrial property offices with the lowest amount of PCT documents to classify a large number of patent documents.