Defines a common interface for the exchange of messages between acquirers or their agents and card acceptors. Specifies the message content, data elements, format, values and structure for data elements. It is based upon the same principles as EN 28583 (ISO 8583) and is intended to be used when EN 28583 is not appropriate. Where possible, data element names and attributes common to ISO usage are employed. Does not include data communication and representation related characteristics such as trailer information, header, protocol and transmission control.