General Information on the
Eighth Edition of the International Patent Classification (IPC)

(WIPO Publication No. 409)

Introduction

When an inventor wishes to have his invention protected, he has to apply to the competent government authority for a patent. In his application, he has to describe his invention. In some countries, the patent application is then published by the said authority, which hereinafter will be called "the industrial property office".

Once the patent is granted, it is usually published in the form of a document by the industrial property office which has granted it. This document contains, with or without changes, the description of the invention furnished by the applicant.

More than 100 countries publish [1]  patent applications and patents - hereinafter called "patent documents" [2] - and in recent years the total number of such documents issued each year has reached nearly two million.

Inventions are made in all fields of science and technology, that is - to use the most customary basic distinction among the three main fields - in the chemical, the electrical and the mechanical fields.

The amount of information contained in patent documents is immense. They contain practically everything that represents an advance in the knowledge of mankind in the field of technology. It is therefore extremely important that this information be accessible to anyone who needs it. Such accessibility exists in theory because the patent documents are published, that is, are made available to any member of the public. But, in practice, accessibility presents great difficulties because of the enormous number of published patent documents and because, as already mentioned, these documents deal with all aspects of technology.

Obviously, what is needed is a system which allows patent documents relating to any particular area of technology to be identified and retrieved.

The International Patent Classification (IPC) is such a system. In its eighth edition, it subdivides technology into almost 70,000 fields or groups. Each group is described in a few words and identified by a "classification symbol" consisting of numbers and letters. The wordings of these 70,000 groups are contained in a publication, entitled the "International Patent Classification". This title is used to designate both the classification system and the publication.

The system works in the following way. Before publication, the patent document is "classified", that is to say, it is assigned - by qualified staff of the industrial property office - the classification symbol or symbols which correspond to the technical field or fields to which the invention described in the document relates. The symbol or symbols are printed or displayed on the front page of the published document.

Any person wishing to know which patent documents contain information on a given technical field only needs to refer to the IPC to find which one of the 70,000 or so terms relate to that field. It is then possible to find all the documents that have been assigned that symbol. This operation is called "retrieval", both in the abstract sense of the word (finding or recovering the information) and in the physical sense of the word (finding the document which contains the information).

The rest of this brochure gives details on the various aspects of the IPC and its operation.

Structure of the IPC

The version of the IPC which has been in force since January 1, 2006, is the eighth edition or IPC-2006. It is the result of IPC revision and reform carried out in the years 1999 to 2005. The following remarks are based on the eighth edition.

The IPC is a hierarchical system and is divided into the following subdivisions: sections, classes, subclasses and almost 70,000 groups (of which approximately 10% are "main groups", and the rest "subgroups").

Each section has a title and a symbol. The title consists of one or more words and the symbol consists of a capital letter of the Roman alphabet. They are as follows:

A	Human Necessities
B	Performing Operations; Transporting
C	Chemistry; Metallurgy
D	Textiles; Paper
E	Fixed Constructions
F	Mechanical Engineering; Lighting; Heating; Weapons; Blasting
G	Physics
H	Electricity

Each class has a title and a symbol. The title consists of one or more words and the symbol consists of the symbol of the relevant section followed by a two-digit Arabic number. For example, the subsection "Foodstuffs; Tobacco" has the following four classes:

A21	Baking; Equipment for making or processing doughs; Doughs for baking
A22	Butchering; Meat treatment; Processing poultry or fish
A23	Foods or foodstuffs; Their treatment, not covered by other classes
A24	Tobacco; Cigars; Cigarettes; Smokers’ requisites

Each subclass has a title and a symbol. The title consists of one or more words and the symbol consists of the symbol of the relevant class followed by a capital letter of the Roman alphabet. For example, class A21 ("Baking; Equipment for making or processing doughs; Doughs for baking") is divided into three subclasses (B, C, D) as follows:

A21B	Bakers’ ovens; Machines or equipment for baking
A21C	Machines or equipment for making or processing doughs; Handling baked articles made from dough
A21D	Treatment, e.g. preservation, of flour or dough for baking, e.g. by addition of materials; Baking; Bakery products; Preservation thereof

Each main group and subgroup has a title and a symbol. The title consists of one or more words and the symbol consists of the subclass symbol followed by two numbers separated by an oblique stroke. The first number has one, two or three digits; the second has two, three, four or five digits. For a main group, the second number consists of two zeros. For example, subclass A21B ("Bakers’ ovens; Machines or equipment for baking") has five main groups (1/00, 2/00, 3/00, 5/00, 7/00), the first two of which are the following:

A21B 1/00	Bakers’ ovens
A21B 2/00	Baking apparatus employing high-frequency or infra-red heating

Main group A21B 1/00 ("Bakers’ ovens") is divided into 19 subgroups, the first four of which are the following:

A21B 1/02	.  characterised by the heating arrangements
A21B 1/04	. .  Ovens heated by fire before baking only
A21B 1/06	. . Ovens heated by radiators
A21B 1/08	. . . by steam-heated radiators

As can be seen from the above example, not all the subgroups are on the same hierarchical level; the highest are preceded by one dot, the lower - according to their level - by two, three, four or more dots. However, the symbol does not indicate the hierarchical level of the subgroup.

In some areas of the eighth edition of the IPC, "hybrid" or indexing systems are provided, in order to improve the effectiveness of the IPC and make it more efficient for the retrieval of documents. In such systems, indexing codes identify elements of information about the disclosure which can be useful for certain types of searches.

 

The Strasbourg Agreement of 1971

The IPC system is the result of an international cooperative effort by the industrial property offices of many countries.

The basis for this cooperative effort was a multilateral international treaty, the "European Convention on the International Classification of Patents for Invention", concluded in 1954 under the aegis of the Council of Europe. In 1967, BIRPI, the predecessor of the World Intellectual Property Organization (WIPO), and the Council of Europe entered into negotiations for the common administration of the continuing work of improving the Classification during a transitional period, and the joint administration of the Classification was commenced in 1969. In 1971, a new treaty was negotiated and signed under the joint auspices of the Council of Europe and WIPO. That treaty is the "Strasbourg Agreement Concerning the International Patent Classification" (the "Strasbourg Agreement"), adopted at Strasbourg on March 24, 1971, by a diplomatic conference of the States members of the International (Paris) Union for the Protection of Industrial Property. Under the Strasbourg Agreement, which entered into force in 1975, the administration of the International Patent Classification became the responsibility solely of WIPO. In other words, the transitional period, which started in 1969, ended in 1975 and brought to an end the responsibility of the Council of Europe with respect to the IPC. The IPC thus became a worldwide system administered by an intergovernmental organization of global scope.

Any country party to the Paris Convention for the Protection of Industrial Property may become party to the Strasbourg Agreement, which confers several rights and imposes several obligations on the State that has become party to it. The most important right is the right to participate in the continuing work of improving the IPC, such improvement consisting in the amendment of the Classification by a Committee of Experts of which each State party to the Strasbourg Agreement is a member. The most important obligation is to apply the Classification, that is, to indicate the relevant classification symbols on each patent document published by the industrial property office of such a State. Providing this information is the responsibility of that office.

The full text of the Strasbourg Agreement is available in the form of a brochure which can be ordered from WIPO (Publication No. 275).

 

IPC Reform

The Classification has been periodically revised in order to improve the system and to take account of technical development. The previous, seventh, edition of the IPC was in force from January 1, 2000, to December 31, 2005.

In 1999, the IPC Committee of Experts recommended, in parallel with IPC revision, to launch the reform of the IPC in order to adapt the Classification to the electronic environment, to increase its efficiency for the retrieval of patent information and to facilitate its use for small and medium-sized industrial property offices and the general public. Substantial changes to the IPC itself and to methods of its revision and use were needed. This recommendation was subsequently endorsed by the Assembly of the IPC Union.

The basic period of IPC reform has been completed in 2005. The eighth edition of the IPC entered into force on January 1, 2006. It already represents the reformed IPC and includes many new features elaborated in the course of the reform. The most important of them are described below.

One of the important features of the reformed IPC is its two-level structure which will better satisfy differing needs of various categories of users. The two-level system consists of a core level and an advanced level.

The core level contains approximately 18,000 entries at high hierarchical levels (classes, subclasses, main groups and subgroups). It is a relatively stable part of the IPC. Revision amendments to the core level will be made in three-year revision cycles when necessitated by technological progress.

The advanced level represents a further elaboration of the core level, i.e., it includes the core level and additional subgroups. Initially, it includes approximately 70,000 entries but its size will rapidly grow since revision amendments to the advanced level will be continuously made through an accelerated procedure under the supervision of a special subcommittee.

Although any industrial property office may choose which level to employ for classifying its published patent documents, it is intended that the relatively simple core level will be used for classifying and searching patent documents belonging to small and medium-sized national patent collections, while the more complex advanced level will be used for classifying and searching patent documents belonging to large collections. In particular, classification at the advanced level will cover patent documents included in the PCT minimum documentation.

The publication of the IPC in paper form will be continued, it will, however, be restricted to the core level, in view of its stability during the three-year revision cycles. The Internet publication contains the complete text of the Classification including the core and the advanced levels and becomes the principal form of the publication of the IPC. The Internet version incorporates the electronic layer, including various electronic data illustrating IPC entries or explaining them more in detail. The electronic layer enhances understanding and facilitates the use of the IPC for industrial property offices and the general public.

Classification definitions for selected subclasses of the IPC are already available in the electronic layer of the eighth edition. They are intended to provide more detailed explanations of the contents of IPC entries than the official text of the IPC. During further development of the IPC, classification definitions will be elaborated for all of the subclasses of the Classification. More than 3,000 structural chemical formulae are available for viewing in the electronic layer of the eighth edition. Their role is to illustrate chemical areas of the IPC by providing a visual graphic representation of the subject matter of the chemical areas. The electronic layer also contains facilities for displaying main groups of the IPC in the standardized order.

One of the objectives of IPC reform was to provide possibilities for performing patent searches with the use of the current version of the IPC only and to eliminate the need to rely on superseded IPC editions. This objective will be achieved by reclassification of patent collections according to revision changes in the IPC.

Access to the worldwide collection of patent documentation will be provided through the Master Classification Database (MCD). It represents a bibliographic database storing all bibliographic elements, including IPC symbols, of patent documents at various publication levels. The database also contains family information. The documents included in the MCD will be classified according to the current version of the core level of the IPC and the continuously updated advanced level. Documents included in the PCT minimum documentation will be reclassified by members of the Special Subcommittee for the Supervision of the Advanced Level of the IPC and some other large industrial property offices. In order to alleviate the workload of reclassification for other offices, their documents having patent family members in the PCT minimum documentation will be reclassified by automatic propagation of the reclassification data from the PCT minimum documentation.

The access to the Master Classification Database will be possible in several ways, for example, via the Esp@cenet of the EPO. The Esp@cenet will use the IPC data present in the MCD.

Many particular rules of the IPC were amended or further specified in the course of IPC reform. This concerns, for example, presentation of classification symbols on the front page of patent documents, priority rules in the IPC, principles of multiple classification, use of hybrid systems and classification procedures for patent documents at different publication levels. A large number of amendments to principles and rules of the Classification made it necessary to completely review and redraft the Guide to the IPC representing the only official handbook on classification. A number of special documents, relating to classification, revision and maintenance of the IPC, and creation of electronic data, have been elaborated during the IPC reform. They are available on the WIPO IPC website.

 

IPC Publications and Electronic Products

As already indicated, the latest version of the IPC - which has been in force since January 1, 2006 - is the eighth edition. Its core level is published in the printed form in four bound volumes. There are two authentic versions, one in English and one in French. Sample pages of both sides of the title page appear as pages 1 and 2 of the Annex to this brochure.

Pursuant to Article 3(2) of the said Strasbourg Agreement, official texts of the Classification may be established in other languages. Complete texts of, for example, the seventh edition of the Classification were established in the Chinese, Croatian, Czech, Dutch, German, Hungarian, Japanese, Korean, Polish, Portuguese, Russian, Serbian, Slovak and Spanish languages.

The Guide to the IPC [ PDF]is published separately in Volume 5 of the printed publication. The main purpose of the Guide is to explain the layout and the use of symbols in the Classification, as well as the principles of the IPC and its interpretation. It also gives advice on how to classify and search patent documents according to the IPC.

Each section in the printed publication is preceded by a summary of its contents, indicating the subsections, classes and subclasses of that section. Sample pages of the three pages constituting the contents of section A appear as pages 3 to 5 of the Annex to this brochure [ PDF].

Each class starts on a new page and is followed by the different subclasses into which the class is divided. Most subclasses are preceded by a summary of their contents, called the "Subclass Index". Page 6 of the Annex to this brochure  [ PDF] shows the first page of a class (class A23) and the core level of subclass A23B.

The Internet version of the eighth edition, in English and French, was published on the WIPO IPC website. Compared with the printed version, the Internet version contains the complete text of the Classification (core and advanced levels) and incorporates the electronic layer including supplementary information facilitating the use of the Classification, such as classification definitions, illustrating chemical formulae and main groups in a standardized sequence. Navigation in the text is possible using the hierarchical structure of the IPC, as well as by direct access to the relevant symbols of the Classification. Hypertext links provided allow to switch between the English and French versions and between IPC places interconnected by references.

Pages 7 to 9 of the Annex to this brochure [ PDF] shows the advanced level (complete text) of subclass A23B.

The use of the IPC is facilitated by a separate publication, the official " Catchword Index". This is a book containing thousands of "catchwords" arranged in alphabetical order. Under most of these catchwords catchword phrases appear, narrowing the meaning of the catchword. Each catchword or catchword phrase indicates the place in the IPC which deals with the subject in question.

Page 10 of the Annex to this brochure [ PDF] is a sample of a typical page of the Catchword Index.

There is one official Catchword Index in English and one in French. Catchword indexes have also been established in other languages in order to facilitate the use of the IPC in those languages.

The official Catchword Indexes to the eighth edition were published in the printed form and on the Internet. References in the Catchword Indexes to the core level of the IPC are distinguished from references to the advanced level. The electronic version of the Catchword Indexes is published as part of the Internet version of the IPC.

Information on how subject matter has been transferred from one place to another in the IPC as a result of the revision work carried out during the seventh revision period (revision of the seventh edition of the Classification) is contained in the Revision Concordance List which is also published as part of the Internet version of the IPC. This is a publication which shows where subject matter of the seventh edition that has been transferred, as a consequence of the revision of that edition, can be found in the eighth edition of the IPC.

Page 11 of the Annex to this brochure [ PDF] is a sample of a typical page of the Revision Concordance List.

Various editions of the IPC are available on the IPC:CLASS CD-ROM. In its latest version (the fourth edition), IPC:CLASS contains the first to seventh editions of the IPC in English and French, the fourth to seventh editions in German and the fifth to seventh editions in Russian and Spanish. Furthermore, it contains the English, French and Russian catchword indexes and a bilingual (German/English) catchword index (the "Stich- und Schlagwörterverzeichnis"), elaborated by the German Patent and Trade Mark Office with the participation of the Austrian Patent Office. The Revision Concordance Lists associated with the various editions are also included.

The retrieval software enables the user to make queries using keywords, classification symbols or combinations of both in any of the data files on the CD-ROM. The user may choose to work (i.e., display menus, prompts and help screens) in any of the above-mentioned languages, can switch between different IPC editions and language versions and can consult the catchword indexes, the revision concordance data or the valid symbols data. The user also has a bridge to a number of online databases and databases on other CD-ROMs, permitting loading of IPC symbols in preformatted files, ready for use when searching in those databases.

A new version of the IPC:CLASS CD-ROM (Version 5) will be published in 2006. This version will contain the complete text of the eighth edition in English and French, including the Catchword Indexes and the electronic layer, and will incorporate facilities enabling downloading of amendments to the advanced level from the Internet.

Various files containing the IPC scheme (core and advanced levels), catchword indexes, Revision Concordance List, classification definitions, illustrating chemical formulae and other IPC-related material, are available in XML format for free downloading from the WIPO IPC website.

 

Use of the IPC for Classifying the Patent Documents of Various Countries

According to the Strasbourg Agreement, patent documents must, as a rule, be classified according to the finest subdivisions of the IPC. However, if, in any country, the procedure for the grant of patents does not provide for a search of the state of the art (to determine, mainly, whether the invention claimed is novel), classification to subclass level is sufficient. Nevertheless, some countries have gone beyond their treaty obligations.

According to information available in January 2006, the following 76 countries and five international organizations applied the IPC to its full extent to their published patent documents, that is, down to the finest subdivision of that Classification (the year in parentheses, appearing, when known, after the name of a country or an organization, is the year from which the patent documents have been published by that country or that organization with the IPC symbols printed on them):

African Intellectual Property Organization (OAPI) (1981)
African Regional Intellectual Property Organization (ARIPO) (1985)
Albania
Argentina (1973)
Armenia (1993)
Australia (1970)
Austria (1969)
Azerbaijan (1993)
Belarus (1992)
Bolivia (1985)
Bosnia and Herzegovina (1994)
Brazil (1972)
Bulgaria (1973)
Canada (1977)
China (1985)
Croatia (1993)
Cuba (1974)
Cyprus (1975)
Czech Republic (1993)
Democratic People’s Republic of Korea (1983)
Denmark (1968)
Egypt (1974)
Estonia (1994)
Eurasian Patent Office (EAPO) (1996)
European Patent Office (EPO) (1978)
Finland (1968)
France (1969)
Georgia (1992)
Germany (1971)
Greece (1985)
Haiti (1987)
Hungary (1970)
Iceland
India (1975)
Indonesia (1992)
Iraq (1980)
Ireland (1969)
Israel (1969)
Japan (1975)
Kazakhstan (1992)
Kenya (1975)
Kyrgyzstan (1993)
Latvia (1994)
Lithuania (1994)
Malaysia (1985)
Mexico (1980)
Mongolia (1972)
Netherlands (1969)
New Zealand (1983)
Norway (1968)
Paraguay (1983)
Peru (1984)
Philippines (1972)
Poland (1970)
Portugal (1978)
Republic of Korea (1979)
Republic of Moldova (1994)
Romania (1970)
Russian Federation (1991)
Serbia and Montenegro
Slovakia (1993)
Slovenia (1993)
Spain (1967)
Sri Lanka (1980)
Suriname (1975)
Sweden (1967)
Switzerland (1971)
Tajikistan (1993)
Thailand
The former Yugoslav Republic of Macedonia (1994)
Trinidad and Tobago (1996)
Turkey (1988)
Turkmenistan (1993)
Ukraine (1992)
United Kingdom (1967)
United States of America (1969)
Uruguay (1982)
Uzbekistan (1993)
Venezuela (1978)
Viet Nam
World Intellectual Property Organization (WIPO) (1978)

Nineteen other countries currently classify their published patent documents only down to subclass level of the IPC (the year in parentheses, appearing, when known, after the name of a country, is the year from which the patent documents have been published by that country with the IPC symbols printed on them):

Bangladesh
Belgium (1955)
Chile (1969)
Colombia (1978)
Costa Rica
Democratic Republic of the Congo (1972)
Ecuador (1985)
Guatemala
Guinea
Honduras
Italy (1970)
Luxembourg (1973)
Malawi (1964)
Monaco (1975)
Morocco
Nicaragua
South Africa (1973)
Zambia (1965)
Zimbabwe

It is estimated that approximately 50 million patent documents have been published so far in the world. Most of them are provided with the classification symbols of the IPC. Currently, the IPC is applied to 95 per cent of nearly two million annually published patent documents.

 

Use of the IPC for the Retrieval of Patent Documents

Industrial property offices need to retrieve the information contained in patent documents for establishing the "state of the art" for any given field of technology at any given point in time, and, on the basis of the state of the art as compared with the alleged invention described in any patent application, to decide whether it corresponds to certain criteria of patentability, mainly whether it is "new" and whether it is "non-obvious". The state of the art is generally discovered by "searching" for (and finding) documents of possible relevance, that is - in the terminology of the Patent Cooperation Treaty (PCT) - "everything which has been made available to the public anywhere in the world by means of written disclosure ... and which is capable of being of assistance in determining that the claimed invention is or is not new and that it does or does not involve an inventive step (i.e., that it is or is not obvious)" (PCT Rule 33.1(a)). (Relevant disclosures may be other than patent documents, but for the purposes of this text only patent documents are considered.)

It is the classification of the patent documents which makes access to them possible. Patent documents bearing the same classification symbols or neighboring classification symbols were earlier generally assembled in what are called "files", and the files most frequently needed by any "searcher" or "examiner" employed by an industrial property office were kept in or near the premises where he works. These files are generally referred to as "search files". When the searcher made a search he scanned the documents contained in the relevant files. Nowadays, examiners mostly use computerized databases which contain bibliographic data (including the IPC symbols), abstracts, titles and the full text of patent documents. The examiner can, from a computer in the office, interrogate one or more of the available databases, using IPC symbols and keywords. The computer identifies patent documents of possible relevance, and the examiner can then consult the full text of those documents, which may be kept in a numerical file, for example, stored on a CD-ROM.

Before the existence of the IPC, the search files were arranged according to the "national" classification used by the industrial property office. The classifications most used were the "American" or "U.S.", the "British" or "U.K.", the "German" and an earlier version of the German, "the old German", the "Dutch" or "Netherlands" and the "Japanese". Nowadays, almost all published patent documents can be searched with the use of IPC symbols.

Before making a search, it is essential to establish clearly the technical subject of the search and identify technical terms relating to this subject. To prepare for searching a technical subject with the use of the IPC, it is necessary to locate in the IPC the appropriate place.

For this purpose, a systematic approach could be adopted and followed step by step, i.e., the relevant section, class and subclass should first be identified and, then, the main group or the subgroup. It is important to remember that the title of each subgroup must be read as being restricted by the titles of the higher level subgroups, the main group and the subclass. Bearing this in mind, it is necessary to select a subgroup with the largest number of dots which still embraces all the essential characteristics of the technical subject.

For the uninitiated user, it is advisable to approach the Classification by using the official Catchword Index to the IPC. This publication contains thousands of catchwords representing technical terms used in patent documentation and technical literature, which are arranged in alphabetical order. The catchword phrases appearing under the catchwords give an indication of subject matter designated by IPC symbols.

An alternative method of direct accessing the IPC is using the natural language search in the Classification provided by the TACSY system. This system is available on the WIPO IPC website and allows to retrieve relevant places in the IPC at three hierarchical levels, subclass, main group and subgroup, by introducing a free text in the query field.

WIPO actively promotes the universal use of the IPC. For example, the IPC is used for classifying and searching in various patent documentation and information centers, such as the African Patent Documentation and Information Center (CADIB), established under the auspices of the African Intellectual Property Organization (OAPI), and the Patent Documentation and Information Centre for English-Speaking Africa, established under the auspices of the African Regional Intellectual Property Organization (ARIPO).

WIPO has assisted, or is assisting, industrial property offices in developing countries to establish information centers for accessing patent documentation.

 

Training on the Use of IPC

WIPO provides intensive training in the use of the IPC for the staff of the national or regional industrial property offices concerned by development projects. WIPO also organizes training courses in the use of the IPC, where experts from industrial property offices or from WIPO instruct in the use of the IPC for classifying as well as for searching. Such training courses, which are usually intended for industrial property offices of a particular region, have been organized, for example in 2005, in Finland, Mexico and Ukraine.
 

Sample pages

[ PDF]

 

[1] In this brochure, "publish" should be understood as including also the "laying open for public inspection" by the industrial property office concerned.

[2] In some countries, forms of protection other than patents are also available (for example, inventors’ certificates, utility models, utility certificates). For the purposes of this brochure, the expression "patent documents" includes also documents applying for or granting such forms of protection.