EDIFACT message guide · Master data
IMPDEF EDI implementation guide definition
The UN/EDIFACT message used to exchange the implementation details of an EDI message, including its usage and presentation.
- Sent by
- Trading partner, industry body or software vendor
- Received by
- Trading partner or EDI software
- Standard
- UN/EDIFACT · Batch message
- X12 equivalent
- No direct equivalent
What is the EDIFACT IMPDEF message?
IMPDEF is the UN/EDIFACT EDI implementation guide definition message. The directory defines it as a message that permits the exchange of implementation details of an EDI message, including its usage and its presentation.
An implementation guide narrows a standard message to what a partner actually uses: which segments and elements are required, which codes are allowed and any extra rules. Exchanging it as data rather than as a document lets mapping tools import the partner's rules and validate against them.
How to read this diagram: the top row shows who sends IMPDEF, to whom, and which messages usually come before and after it. The lower part shows what the directory D.21A itself requires: the envelopes around IMPDEF and the segments and segment groups it marks mandatory. Conditional groups are listed by their trigger segment rather than drawn in full. This is the directory's minimum, not a trading partner's requirement: a message implementation guide, such as an industry subset or a partner’s own guide, usually makes some conditional groups mandatory, restricts the codes and may use an older directory.
When it is used
- Sharing a message implementation guide with partners
- Importing a partner's rules into mapping tools
- Distributing industry subsets
Where it fits in the message flow
No other message routinely comes directly before or after IMPDEF; it is exchanged when the business event occurs. If the partners agree, the receiver confirms each interchange with a CONTRL syntax and service report.
Structure
Mandatory segments in IMPDEF (directory D.21A)
In UN/EDIFACT directory D.21A, the IMPDEF message has 41 segment positions arranged in 13 segment groups. These are the segments and segment groups marked mandatory at message level, in order; a mandatory group is shown with the segment that starts it. Segments inside conditional groups are needed only when the group is used. This is the directory’s requirement, not your trading partner’s: each partner’s message implementation guide names the directory it uses, often an older one such as D.96A or D.01B where the structure can differ, makes some conditional segments mandatory and restricts the codes.
- UNH
- BGM
- MSG
- DII
- UNT
Practical example
IMPDEF in practice
A retailer publishes its implementation guide for invoices. Besides the readable document, it provides the guide's rules as an IMPDEF, which suppliers' EDI software imports to validate invoices against the retailer's required segments and codes before sending.
Implementation
Implementation considerations for IMPDEF
- Keep the machine-readable guide in step with the published document.
- Version guides and state the directory they are based on.
- Check which tools can import the format.
- Tell partners when guides change, and from which date.
How ECOM helps
Automate IMPDEF with ECOM
Solution
EDI Integration
Exchange X12 and EDIFACT documents with partners and integrate them directly with your ERP.
Service
Mapping and Translation
Map development and maintenance for X12, EDIFACT, XML, JSON, flat files and ERP formats.
Solution
Trading Partner Onboarding
EDI certification and automation onboarding for customers, suppliers and carriers, by whichever method each partner can support.
Compare X12 and EDIFACT, or see answers to general questions in the EDI FAQ.
Related messages
Related master data messages
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