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Last seen: 09/18/2022 - 12:12
Joined: 08/30/2022 - 18:05
Field Classification

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: 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: 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!

Last seen: 01/26/2024 - 08:16
Joined: 11/14/2017 - 22:15
see bulk file docs


Pvteam can correct me if I'm wrong but the CPCs come from the patent office's bulk files at  There are docx files there that explain the data.  I believe the sequence zero ones in patentsview are the SymbolPositionCode "F" defining "first" for the sole or first "invention information" CPC.  All utility patents are supposed to have at least one CPC assignment but I have come across patents that do not have them (not all utility patents are listed in the bulk CPC file).  About half of the plant patents have CPC assignments but only assignments for utility patents are in the bulk CPC file, so none of the plant patents in the patentsview database have CPC  assignments.

The USPCs are similar but the patent office has not updated the bulk file of them since 2018, so newer plant and design patents won't have USPC assignments in the patentsview database.  The patent office stopped assigning USPCs to utility patents in 2015 so utility patents issued after that won't have USPC assignments in the patentsview database. There is a similar docx in explaining the data.   The sequence zero USPCs would correspond to the "O" for Original Classification in the U.S. Patent Classification Type Code in the source file.

I hope this helps,
Russ Allen


Last seen: 09/18/2022 - 12:12
Joined: 08/30/2022 - 18:05

Hi Russ,

Thank you for your detailed reply! It is very helpful.

For each sequence number for the CPC patent classification on each patent in 'cpc_current', I mapped the groups to their respective WIPO fields using the crosswalk link provided - - and accounting for differences between the IPC and CPC. 

When I compared my mapped WIPO fields against the WIPO fields provided in the file 'wipo', I found that 1.1 million out of the 7.2 million unique patents had different WIPO fields for sequence 0. The sequence numbers seem to not correspond across datasets and I am worried that there might be some issues with sequence variables in cpc_current. 

Might there be any chance you could help check whether there might be any errors?


Hi PV team,

If you could help on the above, I would be appreciate it very much as well. Thank you!

Last seen: 09/18/2022 - 12:12
Joined: 08/30/2022 - 18:05

Thank you Russ! This is really helpful. I see that they're mapping the CPC technology classes to the WIPO fields for each CPC class sequence on a patent, then reassigning the sequence numbers based on the most frequent WIPO fields. I instead kept the original sequence numbers from the CPC technology classes. 

Dear PV team,

It would be helpful if you could confirm whether sequence "0" is the only main primary CPC classification, or if all the classifications in the 'inventional' category should be considered equal and all primary classifications. Thank you for your help!

Last seen: 09/18/2022 - 12:12
Joined: 08/30/2022 - 18:05

Update: I've used the USPTO bulk files and solved my problems. Thank you Russ for the link!