As previously mentioned, U.S. patents constitute the bulk of documents in the U. S. Patent Classification System. Therefore, class schedules are created and developed by considering the informational content of the U.S. patents in the area of technology that a class is intended to serve. In time, published pre-grant applications, or PGPub documents, will overtake patent grants as the most common document type. Since PGPub documents have neither been searched nor examined, examiners are given more latitude for determining what to classify in them. First, let's look at how patents are classified.
The disclosures of patents are usually multifaceted, and such disclosures are susceptible to varied analyses. To ensure reasonable and uniform placement of patents and to provide for "infringement" type searches, the claimed subject matter interpreted in light of the total disclosure contained in a patent has been selected as the primary basis upon which the informational content of the patent is considered. This narrows down to manageable proportions the subjective judgments that must be made relative to the uniform placement of patents.
Inasmuch as the total disclosure of a patent may include unclaimed subject matter of value, adequate provision is made for including unclaimed subject matter in the system by cross referencing (see Section VI). It must be emphasized that not every item of information included in every patent can or should be provided for. Generally, only unclaimed subject matter characterized as (1) new, (2) uniquely set forth to facilitate recognition, (3) particularly illustrative of significant details or relationships, or (4) providing helpful background or explanatory material, is considered to warrant the placement of additional copies in appropriate subclasses for such subject matter.
This being said, the first step in the process for determining (a) the proper classification of an application for examination, (b) a proper field of search, or (c) the required or "mandatory" classification(s) for an issuing patent grant is to determine precisely what is being claimed.
Each claim in an application or patent must be reviewed to determine which elements or subcombinations are embraced by that claim. Dependent claims frequently add additional subcombinations or elements to the organization claimed in its parent or independent claim. These additional subcombinations or elements could well affect the field of search and application assignment or classification upon issue.
Whereas each claimed invention "as a whole" is treated as invention information for classification purposes, meaning the entirety of all the elements recited in a claim must be classified as a single invention (mandatory classification), some subcombinations of a claim, not separately claimed, may also constitute invention information. In these cases, the inventive subcombination that is not separately claimed should receive a mandatory classification indicating the classification relates to invention information.
Whereas the examined claims of patent grants are classified in the USPC, it is the "invention information" that is classified in pre-grant published applications, or PGPub documents. As the ultimate invention obtained from an unexamined application can never be ascertained with certainty prior to an examination, the classifying examiner is given some discretion in determining which portion of the disclosure to classify in PGPub documents.
What the examiner must classify in these documents is "invention information". Invention information is that portion of the disclosure the examiner feels advances the state of the art in the field of endeavor of the invention. While the claims do not have to be strictly classified in a PGPub application, they should be used as a guide in gauging invention information.
The Primary classification is then assigned to that invention information which, in the opinion of the classifying examiner, most typifies the main inventive concept of the application. It should be remembered that the Primary classification may only be assigned to a primary subclass, i.e., a subclass that can accept the OR classification of a patent grant. In the event the classifying examiner believes there is no disclosure in a document being classified that would advance the state of the art, the examiner is advised to assign the Primary classification for the PGPub document to that subclass in the USPC where, in the opinion of the classifying examiner, it is felt the document would be most beneficial in a search. Secondary classifications are then assigned to all additional invention information disclosure.
The more experienced examiner, or "expert in the art", may wish to additionally classify non-claimed disclosure that would be useful for search purposes, though such classifications are strictly discretionary. Classifications applied to non-invention information should be assigned the Secondary type classification.