Article 26.3 of the Chinese Patent Law specifies a sufficient disclosure requirement: "the description shall set forth the invention or utility model in a manner sufficiently clear and complete so as to enable a person skilled in the relevant field of technology to carry it out." However, there was a great deal of controversy in Chinese patent practices concerning whether or not the State Intellectual Property Office (SIPO) had correctly interpreted this provision for medical inventions, especially the so-called "compound invention", which is an invention simply directed to a compound itself, not to the potential pharmaceutical usage of the compound.