Interchange Definition

​​​​​​​V1.4 30 SEP 2004

An interchange can be defined as a "communication between partners in the form of a structured set of messages and service segments starting with an interchange control header and ending with an interchange control trailer".

NOTE: For use with the Integrated Cargo System an​ interchange may not exceed 10MB in size.

In other words an interchange has three characteristics:

• it is sent from one party to one (or more) other parties as a complete set;
• it is a structured set of messages in the UN/EDIFACT format which are separated by the defined service segments; and
• it starts with the service segment interchange control header (UNB) and ends with the service segment interchange control trailer (UNZ).

The overall structure of an interchange can be depicted as follows:

Note that an interchange may contain multiple messages.

Interchange Service Segments

This section defines those inter​​change service segments that are used in the ICS. Please note that the specific message service segments of UNH (Message Header) and UNT (Message Trailer) are defined for each message used in the ICS and are detailed in the section concerning that message.

UNS Section Separator

The UNS segment is defined as a service segment used to separate Header, Detail and Summary sections of a message, where necessary, to avoid ambiguities in the message segment content. This segment contains one data element. When used to delimit the header section from the detail section, it contains the value "D", and when used to delimit the detail section from the summary section, it contains the value "S". Where the UNS segment is required in an ICS message its usage is defined in the section concerning that message.

UNA Service String Advice

The function of the UNA segment is to define the characters selected for use as delimiters and indicators in the rest of the interchange that follows.

The UNA Service String Advice has a mandatory fixed length of 9 characters. The first three characters are UNA, immediately followed by the six characters that will replace the standard delimiters and indicators in the rest of the interchange.

The ICS uses EDIFACT version 3 syntax rules and hence the inclusion of the UNA segment in EDI interchanges is mandatory to ensure full compliance with the EDIFACT standard.

Consequently the Department adds the UNA segment to all outgoing EDI interchanges.

The Department accepts incoming interchanges with or without UNA segment. It is recommended that software developers include the UNA segment in all interchanges as development schedules allow. The Department will make UNA segments mandatory at some point in the future, preferably after all software developers have introduced the change.

This segment is made up of 'UNA' followed by the six characters below.

UNICSA Interchange Control Structure- (CTLSET)

Introduction:

The Service String Advice, UNA, and the service segments UNB to UNZ shall appear in the below stated order in an interchange.

Notes:

v2.2 (7 November 2002)