Reference
The rules that break real integrations, as far as we have been able to establish them. Almost none of this is published by the platforms that impose it.
Why your Description arrives truncated at 254 characters, why leading zeros vanish from part numbers, and why the schema said it was fine.
The four things everyone gets wrong in an invoice, and multi-country VAT, GST and sales tax with the reasoning shown.
Order confirmation and dispatch, including the rules the DTD cannot express and the buyer enforces anyway.
SAP SRM's Open Catalog Interface: field lengths, the FUNCTION values, and the charset trap.
Found something we have wrong, or a limit we have missed? That is the most useful thing you can send — tell us.