905.03(a) The CPC Database [R-07.2022]

The CPC database maintains technical information regarding the patent family documents for each patent document included. Patent documents contain two types of technical information to classify. These are invention information and additional information. All of the symbols which are allocated to an application, in accordance with CPC guidance, define the application’s classification picture.


A patent family is a group of documents related to each other by common priorities. Examples include a pre-grant publication (PGPub) of an application and any patent issued from the same application. A parent and divisional application also are considered as being in the same family.

In the CPC database, CPC symbols are associated with patent families. When a document is classified in CPC, the symbol associated with the document is stored in the CPC database as an association between the symbol and patent family in which the document is a member. This means that whenever a CPC symbol is allocated to a document all the documents in the family receive the same symbol.

In the CPC database, a document cannot be classified independently of the other documents belonging to the same patent family. Every classification symbol associated with a document, i.e., allocated to the document, is associated with every patent document in the family. Each allocation of a symbol to a patent family has additional attributes stored in the CPC database. These include the following:

  • Classification symbol
  • Type (Invention/other additional information)
  • Position (First/later classification)


All disclosed invention information in a patent document must be classified in CPC in order for a user to retrieve the invention information from the system. Therefore, it is mandatory to classify all the invention information disclosed in each family to be classified.

Invention information is technical information in the total disclosure of a patent document (for example, description, drawings, claims) that represents an addition to the state of the art. The invention information is determined in the context of the state of the art, using guidance provided by the claims of the patent document, with due regard given to the description and the drawings. “Addition to the state of the art” means all novel and unobvious subject matter specifically disclosed in a patent document, which advances the state of the art, i.e., the technical subject matter disclosed that is not already in the public domain.

Patent documents should not be classified as a single entity. Rather, all different inventive entities, claimed or disclosed within the patent document, should be identified and separately classified. Such different inventive entities are represented by different claims, alternative variants or different categories of subject matter (for example, a product and a method of its production).


Additional information is non-trivial technical information which does not in itself represent an addition to the state of the art but might constitute useful information for the searcher. The additional information complements the invention information by identifying the constituents of a composition or mixture; elements or components of a process or structure; or use or applications of classified technical subjects.

Unlike invention information which must be classified, any additional non-trivial technical information that would be useful for search is classified on a discretionary basis.


A C-STAR (C*) is applied to an allocated symbol from the classification picture on an application when that symbol represents at least one concept that is claimed. C* designations should be applied to symbols regardless of type or position (any of family, invention, and additional). No new CPC symbols should be allocated merely to address C*s. Narrow/specific CPC symbols that fall within the claimed subject matter shall be designated as C*. Narrowly allocated symbols that overlap with broadly defined claims shall be designated as C*. There is no limit to the number of the CPC symbols within the classification picture of an application that can be designated as a C*, but at least one CPC symbol must be designated as a C*.

A.Type Attributes

Every classification allocation has a “type” attribute. There are two values that this attribute may have:

  • (A) Invention Information
  • When allocating CPC symbols to a document based on disclosed invention information, the type attribute is set to “invention.” This is typically done by putting the symbol being allocated in the “mandatory” section of the classification form.
  • (B) Additional information
  • When allocating CPC symbols to a document based on disclosed information that is not inventive, the type attribute is set to “additional”. This is typically done by putting the symbol being allocated in the “discretionary” section of the classification form.
  • (C) Position Attribute
    • First – Each patent family will possess a first-listed CPC classification symbol which is selected from the required classifications for the inventive subject matter of the patent family. This “first” CPC classification is the inventive classification symbol which most adequately represents the invention as a whole for the patent family. In situations where a later-published family member possesses a different first-listed CPC classification, this will override the previous first-listed classification (which will be retained for the patent family as an inventive classification symbol). 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.
    • Later – If a symbol allocation is not the “first” position symbol, its position attribute is “later”. All invention allocations that are not “first” position, as well as all “additional” type symbols have the position attribute “later”. All symbols listed on the classification form other than the first listed invention symbol receive the position attribute “later” .