A patent classification is a system for examiners of patent offices or other people to code documents, such as published patent applications, according to the technical features of their content. Patent classifications make it possible to quickly find documents disclosing earlier disclosures identical or similar to the invention for which a patent is applied for.
One of the main advantages of patent classifications is that they enable searching of documents of different languages by using the codes (classification symbols) of the system, rather than words. Patent classification systems were originally developed for sorting paper documents, but are nowadays used for searching patent databases.
A patent classification is fixed under an agreement among people, otherwise it is useless. The International Patent Classification (IPC) is agreed internationally. The United States Patent Classification (USPC) is fixed by the United States Patent and Trademark Office (USPTO). The Derwent classification system is fixed by an enterprise. The German Patent Classification (DPK) was fixed by the German Patent Office (Deutsches Patentamt).
In October 2010, the European Patent Office (EPO) and USPTO launched a joint project to create the Cooperative Patent Classification (CPC) in order to harmonise the patent classifications systems between the two offices. CPC from 2013 replaces the European Classification (ECLA), which was based on the IPC but adapted by the EPO.