EDIFACT Envelope Architecture Description
There are two EDIFACT Envelope levels in which messages may be transmitted. The use of a particular level designates which character set will be used:
- EDIFACT Envelope LEVEL A (UNA): only upper case; only printable characters
- EDIFACT Envelope LEVEL B (UNB): upper and lower case; includes non-printing characters for delimiters
The UNA Interchange is transmitted as a single string of 9 characters prior to the UNB Interchange segment. A release character is used when there is a need to transmit a message in which a character is designated as a delimiter, indicator or terminator, but it also represented in the message data.
EDIFACT has two required levels of envelopes:
- Interchange (UNB/UNZ): a set from one sender’s mailbox address to another sender’s mailbox address
- Message (UNH/UNT): the envelope around one particular message
In addition, there is one optional EDIFACT Envelope level: Functional Group (UNG/UNE). It is used to group like messages together and for sub-addressing within an organization. In the US ANSI X12 standards, this group level is where the message format and version are specified. Use of the UNG/UNE is mandatory to/from North America.
The Message in EDIFACT Envelope
The innermost envelope level is around each message. It is defined by the UNH/UNT segments. The UNH segment has four data elements:
- Message Reference Number (M): assigned by the sender’s computer and is part of the CONTROL mechanism.
- Message Identifier (M): Composite which identifies the message being enveloped using the six character message code (e.g., PAYEXT, REMADV) and the Version/Release data.
- Common Access Reference Number (C): Relates multiple transactions together.
- Status of the Transfer (C): Sequences a series of related messages.
The UNT segment has two data elements:
- Number of Segments in a Message (M): count of segments in the message (including UNH and UNT).
- Message Reference Number (M): same one that was used in the UNH for that particular message.
The Common Access Reference Number is used to identify a series of related EDIFACT messages. For example, one purchase may involve a message exchange that requires four messages to accomplish the complete business transaction.
For Message #1: UNH+2348+ORDERS:D:94B:UN+10381+1:C’
For Message #2: UNH+156009+DESADV:D:94B:UN+10381+2’
For Message #3: UNH+156078+INVOIC:D:94B:UN+10381+3’
For Message #4: UNH+2451+REMADV:D:94B:UN+10381+4:F’.