4.2.2.6.4 Guidance about C-Sets Information in Scheme and Definitions

Date Published

Instructions about the C-Sets construction and syntax are presented in a standard format in all C-Sets authorised subclasses.

As a general guidance, the specific C-Sets rule is located at only one place of the base symbol in the definitions. The placement of the specific C-Sets rule follows the CPC scheme hierarchy. If the C-Sets rule is applicable to all groups of a subclass, it is located at the subclass level only. If the same C-Sets rule is applicable to multiple groups or subgroups within the same subclass, the C-Sets rule is placed at the highest group or subgroup of the multiple groups. A reference usually is placed in the lower groups, indicating the location of the C-sets rule.

With respect to the presentation of C-Sets information in the CPC, first, in the Scheme, a Note at the subclass level states the use of C-Sets in the subclass, and also refers to the Definitions for the detailed C-Sets rules. As further notification, a similar Note may be also placed at the specific group level where C-Sets are applied.

Secondly, in the Definitions, specific guidance about the intended usage and syntax of C-Sets is detailed in the section “Special rules of classification”.

At subclass level, a table indicates the pertinent types of C-Sets using symbols of the subclass as base and/or subsequent, and the place where the corresponding C-Sets rule can be found.

Example: summary of all C-Sets in subclass C12Q

Base Symbols

Subsequent Symbols

C-Sets Rules

C12Q1/68-C12Q1/6874, C12Q1/6897, C12Q1/70

C12Q2500/00-C12Q2565/634

C12Q1/68

C12N15/10-C12N15/1096

C12Q2500/00-C12Q2565/634

C12N15/10


  • As shown in the above table, there are two types of C-Sets in C12Q.
  • In the first type, both base symbols and subsequent symbols are from C12Q and the C-Sets construction is explained in the “Special rules” of C12Q1/68.
  • In the second type, the base symbols are from C12N, while the subsequent symbols are from C12Q and the C-Sets rules are in the “Special rules” of C12N15/10.


Finally, at the subclass, group or subgroup level, the specific C-Sets rules describe the detailed information about the C-Sets construction and the associated syntax.

C-Sets rules are presented with the following three subheadings under the heading Special rules of classification:


  • C-Sets statement
  • C-Sets syntax rules
  • C-Sets examples


The C-Sets statement indicates which technical features are classified in the base and subsequent symbols of the C-Sets.

The C-Sets syntax rules specify the number of symbols in a C-Set; whether duplicate symbols and breakdown codes are allowed or not; the relevance of the order in the string of symbols; and any other special rule relevant for the C-Sets in question.