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Examiner's Handbook Chapter - Two: Aids to Searching or Placement

Chapter Table of Contents



The procedures used to make an accurate and efficient search or to classify a patent document require familiarity with and use of the following search tools: 

  • Index to the U.S. Patent Classification System
  • Manual of Classification
  • Classification Definitions
  • Classification Orders
  • Automated search tools - EAST and WEST

 A. Index to the U.S. Patent Classification System

The Index to the U.S. Patent Classification System System comprises an alphabetical listing of technical and common terms representative of arts, processes, machines, manufactures, compositions of matter, etc., associated with a numerical reference citation to a class or subclass in which potentially pertinent patent documents or literature (non-patent literature) may be found. The Index may be used to find clues to the classification of specific subject matter. The reference cita­tions obtained by using the Index are not exhaustive and only serve as a guide to the sched­ules, or portions thereof, of the identified classes. The definitions and notes (see Subsection C below) associated with these classes or subclasses must be reviewed for more precise information on the location of rele­vant art. This is true even though the reference citation given by the Index appears to state a restricted area of subject matter. Also, synonyms can be used to locate an entry in the Index.

 B. Manual of Classification

The Manual of Classification is comprised of the following documents:

(1) Class Origin Dates.

(2) Overview of the Classification System.

(3) Classes Within the U.S. Classification System Arranged by Related Subjects (CABRSM) - a theoretical organization of all the classes into four major groups and, within each group, an attempt to list the classes in a hierarchy.

(4) Classes arranged by Art Unit.

(5) Classes Arranged Numerically with Art Unit and Search Room locations.

(6) Classes Arranged in Alphabetical Order.

(7) Class Schedules -- a hierarchical arrangement of the subclass titles and numbers organized under each class title.

The Manual of Classification documents are available electronically through the PTO Intranet.  PALM also provides some of the information listed above.

Class and subclass titles are used to identify major and minor segments of the classification system, respec­tively. These brief titles are as suggestive as possible about the subject matter covered by each segment. Therefore, it is best not to depend on class and subclass titles alone to delineate the subject matter in a class or subclass. Reference to respective definitions and notes is essen­tial. If a search or placement is to be expeditious, accurate, and complete, the Manual of Classifica­tion should be used to help find further pertinent information provided for in the relevant class or subclass definitions and appended notes.

 C. Classification Definitions

The Classification Definitions comprise detailed descriptions of the art found in the classes of the Classification system of the USPTO. Used in conjunction with the schedules found in the Manual of Classification, definitions establish placement of each original and each mandatory cross-reference of a U.S. patent. Also, they assist the assignment of each patent application within USPTO.

The review of class and subclass definitions is essential to properly place a document in the USPC system or to obtain a proper field of search therefrom. Each definition consists of a statement of the scope embraced by the respective segment of the system that it delineates.

A subclass definition must be read in light of the class definition and any parent subclass definitions from which it depends. Many of the definitions have accompanying notes. These notes are usually (1) notes that supplement definitions by explaining terms or giving examples and (2) notes that refer to re­lated disclosures located in other classes or subclasses.

The latter notes are termed “Search Notes” and help to qualify and explain the limits of a class or subclass. They generally state the relationship to, and difference from, other iden­tified subject matter collections. For any search or patent placement, each note provided should guide a user to the extent necessary to reach a decision either to include or exclude an area containing relevant subject matter. Search Notes found in the class definition, as well as in the definition of any parent subclasses from which a subclass depends, should also be used as a guide in reaching this decision.

The definitions and notes of each revised class, published in separate Classification Orders, are iden­tified by the class number and title. Class and subclass definitions are available in electronic format, on PTONet. Individual Classification Orders are available from the Classification Home Page at:  http://ptoweb:8081/orders/index.html.

 D. Classification Orders

At the end of a reclassification project, a Classification Order is issued. Classification Orders are issued throughout the year. The Classification Order is a report on the changes to the USPC system brought about as the result of a reclassification project. It also serves to bridge the gap between the date of the Order and the time that the regular paper and electronic search tools are updated to reflect the reclassification. The date of the Classification Order is also the “Issue Date” of the reclassification project.

The following search tools are updated by a Classification Order:

(1) Manual of Classification. Changes to all affected parts of the Manual. This includes any new class schedules or changes to existing class schedules impacted by the project.

(2) Classification Definitions. Changes to the Definitions necessary to support the changes caused by the reclassification project.

(3) Source and Disposition Pages. Lists how art from abolished subclasses has been placed into newly established or existing subclasses.

(4) International Patent Classification (IPC) Concordance. Shows the relationship between newly established subclasses and their IPC counterparts.

(5) Foreign Patent Art Collections. Listings created to provide for foreign patents that were not reclassified as part of the project appear at the end of the Class containing the new schedule. Foreign Art Collections are identified by the prefix “FOR” followed by a 3-digit number. See “Search System Organization,” above, for a more detailed explanation of this practice.

A Reclass Alert Report, issued quarterly, summarizes changes resulting from reclassification orders and notifies examiners of issued reclassification projects. (For a copy of a Classification Order, go to: http://ptoweb:8081/orders/index.html.)

See below for a discussion on how to use the Electronic Search Systems to find the locations of new classes and subclasses of art that were classified in an abolished subclass.

 E. Electronic Search Systems 

The electronic search systems at the USPTO include both word searchable text databases of documents and image searchable databases of documents. The text databases include full text of U.S. patent documents back to around 1971, as well as English abstracts for many foreign patent documents. Additionally, there is an OCR file of older U.S. patent documents that is word searchable. The text searchable databases are referred to as BRS, and the clients on Examiners’ workstations used to access BRS are known as EAST (Electronic Assisted Search Tool) and WEST (Web-based Examiner Search Tool).  

The images for all U.S. patent documents, as well as those of many foreign patent documents, are retrievable for viewing by examiners from their workstations using either of two electronic search clients, EAST and WEST. Images of all U.S. patent documents, and many foreign patent documents, are retrievable by USPC classification from the search clients.

The electronic search systems can be used to access the online database that contains the full text files for all of the U.S. patents issued since 1971.

The electronic search systems can also be used to determine the new location of art classified in a subclass that was abolished in a reclassification project. By searching in one of the Issue Classification Indexes (e.g., CIOR and CIXR) for the abolished subclass, and then analyzing the current classifications of the result set.


The intranet site http://ptoweb/patents/opa/  has EAST and WEST users manuals, training materials, and other training resources.

The underlying textual database, BRS, requires that all patent documents have at least one valid classification. Class 1, subclass 1 is a holding place for patents having no valid classification data — neither OR nor XR. Invalid classifications result for two reasons: (1) the classification may become invalid when a project becomes official and all the old classifications are abolished; (2) the issue classification — that is, the “Blue Slip” classification — may be invalid. These discrepancies are routinely corrected.


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