In certain CPC fields, the examiner has the ability to create and search on combinations of CPC symbols (provided as groupings of symbols), each symbol in a grouping has a defined relationship to the other symbols in its grouping. These groupings are termed combination sets, and provide an enhanced mechanism for storing and retrieving classification information from patent documents. While the usage of CPC combination sets is confined mostly to the chemical fields, there are numerous instances where combination sets are used in mechanical and electrical fields.
The first symbol in a combination set is termed the base classification symbol, and determines the authorization for creation or deletion of combination sets within the field of the base symbol. The other members of a combination set possess the same Invention or Additional information, i.e. INV/ADD attribute as the base symbol, with an ordered ranking to denote their positioning within the combination set.
Guidance on the creation of combination sets is detailed in the CPC classification definitions. For example, the combination sets in a given field may denote the sequence of operations in a multi-step process, while in another field, the combination sets may denote the product and its method of manufacture. It is even possible to have the same CPC symbol appear more than once in a given combination set, with the ordering thereof to reflect the occurrence of multiple steps provided for by the repeated CPC symbol.