This part of ISO 15022 consists of:
-  the description of the Enhanced ISO 7775 syntax and message design rules;
-  the contents and organization of the dictionary of Enhanced ISO 7775 and EDIFACT fields for securities messages; and
-  the contents and organization of the catalogue of securities messages built in the Enhanced ISO 7775 and EDIFACT syntaxes.

It refers to the EDIFACT syntax when necessary to ensure an easy cross-reference between Enhanced ISO 7775 concepts and EDIFACT concepts. The EDIFACT syntax is not described in this part of ISO 15022; it is defined in ISO 9735 which is incorporated by reference.

This part of ISO 15022 is used for electronic data interchange between securities industry participants, independently of the communication network. Network dependent rules, for example, on how to specify where and when the message is to be sent, message acknowledgement and message protection are outside the scope of this part of ISO 15022.

The maintenance of this part of ISO 15022 is described in part 2 of ISO 15022.