This introduction aims at addressing the basic questions of convention and implementation of the EDI technology.  I have a list of topics, and hope that over time I can cover all of them.  I also hope that people reading here may have questions that I haven’t thought to write about.  Please let  me know what your questions are and I will see what I can do about providing answers.

• What is EDI?
• Parts of EDI
• Segments
• Delimiters
• Conventions of EDI
• Why are there more than one version of EDI?
• Standards and Usage
• Encoded Values
• EDI in Good Form
• Element Notation
• Wrapped and Unwrapped EDI
• Enveloping Part One
• Enveloping Part Two – ISA
  
• Enveloping Part Three – GS
• Enveloping Part Four – ST
• Loops in EDI
• Hierarchical Levels

Of course understanding how EDI presents and represents data is the first step.  From here we may want to go to our Data Mapping Guide, or if we are familiar with mapping there are some examples in our mapping case studies of EDI to and from other formats.  Again, if you have an interesting problem or solution, I would love to here about it.  Please send it to
roy@TheIntegrationEngineer.com and I will see what I can do.

Document Identifier

The document Identifier is not encoded.  That is to say, for an 850 the ST document ID is “850″.  For an 810, the Document Identifier is “810″ and so on.  Thus if you open an EDI file, and don’t recognize the GS_01, skip to the ST_01 and it will tell you what standard you will need to find to read this document.

Good form would dictate that the GS_01 and the ST_01 would specify the same type of document.  The GS would specify it on a functional level, and the ST on the standard level.  Thus they would not be identical strings but would indeed convey the same message about what the document(s) would be.  Some EDI translator or processing software will validate this relationship and some may not.  But in the end consistency is the best policy.

Control Number

The control number is different for the ST than we saw in both the ISA and GS.  The ST_02 is a 3 to 9 digit number.  This means that it will start with 001 not 000000001.  Of course you can still use a 000000001 but don’t be surprised when you see less than 9 digits in the ST-SE control number.  Whichever you chose, you must do the same for both the ST and SE.

(Using 000 or 000000000 may be allowed, but is not recommended as any application that trims the zeroes will get an empty string and produce an error.  Be nice and only use values greater than zero.)

Segment Counter

The SE segment counter is the part of the ST-SE that gives people hand editing an EDI document the most trouble.  If the counter is inaccurate it indicates that the document is corrupted.  This should fail in all good translators as processing a corrupt EDI file is saying, “Its okay if we get bad data.”  This counter represents the number of segment between the ST and before the SE.

And it is just that simple.  Remember that you can have more than one GS-GE envelope inside an ISA-IEA, and you can have more than one ST-SE inside a GS-GE, but you can only have one document of one type in side a ST-SE envelope.

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For an overview of Enveloping go here.

Looking for the ISA enveloping page?

Looking for the  GS enveloping page?

Looking for something else relating to EDI?  Check out the EDI Primer post