Hello PV team,
May I check whether there is a single primary technology class / subsection for each patent for the CPC classification? In the cpc_current dataset, many patents have several categories which are inventional. On a related note, could I also check what the sequence of fields might mean on a patent, i.e, what the variable "sequence" in the cpc_current, wipo, and uspc_current means? I am guessing that the sequence variable with value "0" indicates the primary classification, but wanted to check as this is critically important for my study.
The older USPC guidelines mention that each patent has a unique primary technology class - see 1.4.3 here: https://www.uspto.gov/sites/default/files/patents/resources/classification/overview.pdf which says: "Every U.S. patent must have one—and only one—principal mandatory classification known as an OR classification."
The CPC guidelines seem to suggest this unique primary technology class as well - see 905.03(a) III here: https://www.uspto.gov/web/offices/pac/mpep/s905.html which says "There is one and only one "first" position attribute per patent family. The first attribute is associated with the invention symbol that most completely covers the technical subject matter of the disclosed invention. The first position symbol is identified as the first mandatory symbol listed on the classification form."
Thank you for your help!