Additional Content for the ISO 20022 Message Definitions

The purpose of externalising these codes is to be able to update the code sets (for example, add new codes) without impacting the messages themselves and, hence, without requiring the development of a new version of the messages that use these code sets.
Unlike other ISO 20022 code sets, the codes are not included in the message schema with the message element they type.
The ISO 20022 messages use external code sets which are validated and approved by the SEGs.

A Data Source Scheme (DSS) is a mechanism which allows an industry body to specify the use a proprietary code set that is not owned nor managed by ISO 20022, and that replaces a standard code set (either a specific ISO 20022 managed code set or another ISO standard code set, e.g. BICs or ISINs) in specific ISO 20022 Message Components, where the use of such DSS has been approved.

Some ISO 20022 message definitions include a 'SupplementaryData' component that can be used by communities of users to add information to a message that is not catered for by other components of the message definition.

A "variant" is a restricted version of a global message definition.

It requires the development of a specific ISO 20022 message model that eliminates all the unnecessary elements of the global message definition and replaces the components that are restricted by new derived components.