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E-Commerce and E-Business

CEFACT is the UNOs coordinating policies and technical development to support
trade and electronic business.

4.3.1 Interchange Structure
EDIFACT consists of a hierarchical structure where the top level is referred to as an interchange
structure, and bottom levels contain multiple messages. These messages consist of segments, which in
turn consist of composites. This structure indicates the beginning and end of the organizational units of
information within the message but does not contain data relevant to the EDI transaction. It indicates
the sender of the message, the intended recipient, the date and time of transmission, and so on.
The other type of control segment is connected with the loops of segments that may be repeated within
a message. In case of a particular transaction, if the billing address of various parties is different from
the shipping address, then a loop may be used to indicate the names and addresses of various parties in
that purchase order transaction. The loop header and loop trailer segments indicate the start and the
end of the loop. A group or segment can be mandatory (M) or conditional (C) and can be stated to
repeat.

C99 indicates between 0 and 99 repetitions of a segment or group, while M99
signifies between 1 and 99 repetitions of a segment or group.
Segments which initialize with the UN are called the service segments. These segments constitute the
envelope or the packaging of the EDIFACT messages.
EDIFACT consists of service segments like:
1. Envelopes (UNB-UNZ, UNG-UNE, UNH-UNT)
2. Delimiter String Advice (UNA)
3. Section Separator (UNS)
An EDI message includes a field definition table that gives information about the data elements in the
message such as, whether an element is mandatory or conditional, numbers of characters it has, and
whether it is numeric or alphabetic. The structure of an EDIFACT message under the ISO standard is
shown in the figure 4.3. The UNA segment explains the separator characters used in the transmission.
The UNB segment detects the sender and receiver of the transmission and specifies the used character
set. The UNG and UNE segments are used only if the transmission carries many groups of messages of
various types. UNH and UNT segments are the mandatory segments. These two segments are the
collection of other related segments. The UNZ segment ends the transmission.

Figure 4.3: Interchange Structure

Source: http://en.wikipedia.org/wiki/EDIFACT

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