EDI standards are maintained by groups that take input from industry and promulgate standards.   Today, there are two major standards: ANSI X12 is maintained by an organization nearby, in Northern VA, Data Interchange Standards Association.  DISA is the 'Secretariat' that maintains and publishes this set of standards using meetings and methods of ANSI, American National Standards Institute.  EDIFACT is another standard for exchange of business documents, more European in flavor.  Here's a website about UN/EDIFACT.

Here's a tutorial website maintained by Global Exchange Services that gives an excellent overview of both X12 & EDIFACT, and also gets into XML as it's used in EDI. 

The pages handed out in class are from DISA's Introduction to EDI.  The standard set is $400+ to purchase but is well worth the price as it is a set of binders or CDs that contain specifications of a perfectly normalized record structure suitable for documenting any type of transfer of goods & services, or data about, before, during, and after these events.  The handout in class shows a few details for #810/Invoice and #997/Functional Acknowledgement.  These are two of dozens of standards. 

There are other 'players' important in EDI.  Inovis is a large service bureau used by manufacturers, distributors, and buyers for fashion & other 'department store' type goods.  These trading partners hold one another to the Voluntary Inter-Industry Commerce Standards (VICS) and this is their EDI bible.  Here is an example of their emerging standards for Bills of Lading.

Book Distributors & Sellers use a standard called BISAC which is a subset of X12 devised by The Book Industry Study Group.  Industrial customers and suppliers use yet another.  Banks and Financial Institutions use subsets that move the Tender about the orders.  I've learned recently that Health Insurance providers are moving toward an X.12 standard.  

X.12 standards permeate all these electronic trading partnerships and keep it from being a Tower of Babel circumstance.  Any Vertical enterprise application will be of more value if the particular standards of EDI for its core activities are accommodated easily by its enterprise engines.

Standards are folded into other standards.  Here's how the Uniform Code Council's UPC barcodes get into X12 documents about goods headed to a Department Store...

Inovis maintains a central catalog used for EDI trading partners.   They have been in the business since long before the Windows desktop and their services have been accessed for years by users of ascii terminals entering orders in unix, mainframe, or proprietary minicomputer environments.  For their buyer-customers they provide a central database of exactly what is available from their vendor- customers and what the barcoded UPC will be when it arrives at the loading dock.

UCC, The Uniform Code Council, provides the service of registering the UPC, Universal Product Code, barcodes that are practically universal for products headed our way.  Manufacturers & distributors manage their range of UPC codes and this forms one of the data elements in the ANSI standard QRS catalog.  EDI purchasing documents refer to these same #s so nobody is confused.

UCC also defines the format of the UCC-128 barcode label that is the 'carton level identifier' affixed to each carton shipped by UPS, FedEx, or other common carrier when trucking is involved in the distribution. The ID of the UCC-128 barcode becomes one of the data elements in the shipping manifest that is sent via EDI.  When the carton arrives at the loading dock the distribution system already knows its contents and their destination.

When there's air freight or ocean shipping involved there are other standards that apply and other organizations involved in the design and details of these documents and labels.  

The ANSI Standard X.12 is quite complete and defines 10s of 1000s of separate codes used in 1000's of data elements used in 100s of data segments to form dozens of transaction sets for practically any transaction, acknowledgement, confirmation, enquiry, or update required in commerce.  

Industry groups get together to pick and choose the particular standards needed to reflect their commerce.  The Department of Defense, for example, chose these a few years back as they added EDI to their order processing legacy:

840 Request For Quotation
997 Functional Acknowledgment
843 Response To Request For Quotation
832 Price/Sales Catalog
850 Purchase Order
855 Purchase Order Acknowledgment
824 Application Advice
860 Purchase Order Change
836 Contract Award Summary
865 Purchase Order Change Acknowledgment
838 Trading Partner Profile
869 Order Status Inquiry
864 Text Message
870 Order Status Report

Vendors wanting to woo the DOD had best make sure that their flavor of EDI package can support the whole range or they'll be nixed by some Sergeant who isn't getting a snappy 997 & 870 for his 869.   It's interesting to note that the DOD, as of this listing, has left out the whole range of documents that form the Advanced Ship Notice functions, in which carton contents are manifested and forwarded to the shipper for their application of delivery advice.

BISAC uses a subset of X12 which includes six documents.

The nature of EDI transmissions is changing to take advantage of The Internet, but some of EDI still travels via the VANs (Value Added Networks).  It is bound to be an interesting decade for EDI trading partners.