F-term classification: Japanese patent classification

There are 3 classification systems for Japanese patents: F-term, File Index (FI), and IPC. Most professional searchers consider F-term the most precise system in terms of Japanese patent documents.

F-term classification:
F-term is a system for classifying patent documents at JPO according to the technical features of the inventions described in the claims and specifications. F-term is not a replacement for International Patent Classification (IPC) or another unique Japanese patent classification system: FI (File Index), but complements IPC and FI systems by providing a means for searching documents from different viewpoints. We often uses F-term.

The F-term system was developed in 1987 by the Japanese Patent Office (JPO) and is maintained by the same body. The F-term system is used by examiners in the JPO who give appropriate F-terms, together with IPC categories, to each patent document published by the JPO. The IPC system is similar to the scientific classification of organisms; both being hierarchical classification systems based on a single viewpoint. In contrast, the F-term system is like a picture book that presents various views such as "lives in rainforests" or "creatures having wings". The IPC system could be said to be systematic, while the F-term system is intuitive.
The F-term system was developed on the principle that computers will be employed for finding documents using the system.

The F-term classification system consists of themes and terms.
The coverage area of the IPC is divided into approximately 2900 themes with each theme spanning a range of IPC subgroups. A theme is identified by the title describing the range or the theme code which consists of five digits allocated uniquely to each theme; for example, a theme spanning IPC range A01K 87/00–87/06 is identified by its title "Fishing rods" and its theme code is 2B019. Some themes only span one IPC subgroup, such as theme 2F011, "Tape measures" which covers IPC G01B 3/10.
Each theme has a number of viewpoints and each document is classified repeatedly for each viewpoint in the respective theme. For example, theme 2F011 "Tape measures" has the following four viewpoints: tape measures, housings, driving of tape measures and accessories.
From each viewpoint, documents are classified into several groups and labeled with a four-digit code called the term or F-term. For example, from the viewpoint "tape measures", which focuses on measuring tape itself rather than winding mechanism or housing of tape, all measuring tape documents are classified into eight groups such as AA02 "scales for special applications", AA05 "tapes with cores containing synthetic resins", etc.

Pros and cons:
F-term is a more precise system as comparing with IPC. However, because some F-term sheets of practical use are fairly large and complicated like 2H171 and 3C007, examiners sometimes drop applicable F-terms by mistake when they classify documents. In addition, some documents are classified into inappropriate IPC and therefore do not have any appropriate F-terms.

Taking these errors into account, a "defensive" search is conducted by:
• using text keywords as well as F-terms or IPCs;
• calculating union rather than intersection of F-terms; and
• using several F-term sheets that are different but describing similar technologies at the expense of additional time for browsing more documents.

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