The following provides examples of possible strategies for searching using classification symbols. In-depth examples are included below. It is highly recommended to use the CPC as a starting point and primary patent search tool for classification searching (for example, strategies 1 - 3).

Approximately 40 million documents in AbS/Espacenet have CPC symbols. There are multiple ways to search using the CPC in AbS or Espacenet and each technique has a place in a complete search. The CPC suits a staged and iterative approach to searching the prior art.

The five strategies are shown in the diagram with a decreasing level of preciseness. Strategy 1 is the most precise and Strategy 5 is the least precise. In an iterative searching process, the key is to start with a more precise approach and slowly expand the search as needed.

Strategy 1 - CPC-only search

When to use

The CPC symbol or combination of CPC symbols is precise enough that it provides good coverage of the inventive aspects of an invention for the purposes of a search. No keywords are needed, meaning that foreign language documents can be easily found. The number of results with a narrow CPC search can also be reasonable in terms of performing an efficient search.

Advantages:

uses only CPC symbols, no keywords;
locates documents without an abstract (old US documents); and
locates non-English documents, particularly in DE and FR collections

Coverage

Using this strategy, the search will cover approximately 40+ million documents classified in the CPC, including full EP, US, WO, GB, DE, FR collections and parts of other national collections including CN, KR, AU, and CA.

Example Syntax

Step: Enter selected CPC symbol(s) in the AbS marker window

Searching for circulation control around a wing:

A: B64C3/141/c – focussed search of 105 docs
Searching for connector for a baby basket that fixes to a pram and to car seat attachment:

A: B62B7/142/c AND B60N2/2821/c - focussed search at the ‘intersection’ of technology

Note to always consult definitions, warnings, and notes if they are available.

Strategy 2 - CPC and keywords in abstract searching

When to use

Strategy 2 may be employed when a first iteration did not yield highly relevant prior art. It should also be used when the CPC definition is of a wider scope than the claimed invention or the number of documents classified under the CPC symbol(s) is too large for an efficient search.

Aim

With this strategy, the aim is to use both English language abstracts and Derwent abstracts (in WPI) of CPC-classified documents. Some documents from collections such as DE, FR, or old US, may not have original English abstracts but their records in WPI may contain Derwent English abstracts.

Disclosures in Derwent abstracts are generally more useful as they are prepared by subject matter experts who read the patent document and summarise the disclosure in a structured form that identifies the inventive concept and advantages over the prior art. Original abstracts, on the other hand, are prepared by applicants and generally use subjective or irregular language and may not always explain the inventive concept in a precise or consistent manner.

Coverage

Full EP, US, WO, GB, DE, FR collections and a small part of national collections CN, KR, AU and CA (documents with an original abstract and/or a Derwent abstract only).

Example Syntax

Searching for a bar code scanning system with autofocus:

A: G06K7/10722/c/low

B: (auto_focus)/ab

Strategy 3 - CPC and keywords in full text

When to use

Strategy 3 is useful when Strategies 1 and 2 do not produce highly relevant prior art, or when features being searched are unlikely to be disclosed in abstracts. In essence, the CPC limits your search to the inventive concept, and the keywords tease out the specific arrangement of the claimed features. Some common situations where this is useful include:

specific embodiment of a combination of chemical compounds
precise arrangements of mechanical components such as those found in machinery and electrical systems.

Aim

In this strategy, the aim is to utilise the full disclosure of English documents.

Coverage

CPC-classified documents that have full text in English, especially EP, US, WO and GB.

Example Syntax

Search for glow in-the-dark golf balls:

A: A63B37/0022/c/low

B: glow+, +luminescent

Strategy 4 - IPC, CPC, and keywords in abstract searching

When to use

Strategy 4 is useful when highly relevant prior art has not been found and the search is now expanded to using the IPC and CPC at the same level in the hierarchy with the IPC. The warnings state a reclassification is occurring and less precise CPC symbols should be searched (a consequence is the search needs to be expanded to more general and less precise CPC symbol(s)), and to search non-CPC classified material using the IPC (for example Japanese documents, prior to 2016 Chinese documents, Russian documents, and portions of Korean and Australian prior art).

In some technologies the CPC does not offer a more granular breakdown and you may have to start searching at this level. A further scenario is where you’ve exhausted the documents classified in the CPC and simply need to search those documents only classified in the IPC. Because of the broader nature of the IPC, you are likely to need to use keywords.

Whilst AbS scores documents that have markers found in the abstract higher than documents with markers in the body of the specification, limiting your search to the abstract minimises the risk of unwanted terms in the specification overpowering the scoring algorithm – resulting in a higher score for these unwanted terms.

Aim

In this strategy, the aim is to search in collections with incomplete or no CPC classification, especially unique collections from Australia, Canada, Korea, Japan, and China.

Coverage

Non-CPC documents, especially unique collections of AU, CA, JP, CN, and KR

Example Syntax

Searching for temperature control circuit in a vape that monitors resistance during the usage cycle:

A: A24F40/57/ic/c

B: resistan+/ab

C: cycl+/ab

Strategy 5 - IPC, CPC and keywords in full text

When to use

Strategy 5 is useful when the search needs to be expanded to broader CPC symbol(s), at the IPC-equivalent level. If your keywords are particularly important to the search but are not likely to be found in the abstract then you will need to search the full text. In essence, the classification limits your search to the inventive concept, and the keywords tease out the specific arrangement of the claimed features. Some common situations where this is useful include:

specific embodiment of a combination of chemical compounds.
precise arrangements of mechanical components such as those found in machinery and electrical systems.

Aim

In this strategy, the aim is to search in collections with incomplete or no CPC classification but with full text description in English.

Coverage

Documents without CPC symbols but with full text in English, especially unique collections of AU and CA.

Syntax

Searching iteratively for different ways electric propulsion is used in space vehicle control:

A: B64G1/26/ic/c/low

B: electric propulsion

C: arc_jet

D: ion thruster

Amended Reasons

Amended Reason	Date Amended
Updating information to reflect AbS as search tool	30 Jul 2026
Accessibility fix – alternative text for images	22 Oct 2025
	18 Oct 2023