AAIs and the Business Unit.Object.Subsidiary account key encode the entire accounting model.
The defining translation
JD Edwards derives accounting from Automatic Accounting Instructions — short mnemonic keys resolved by company and document type — and writes every posting into a literal three-part account key of Business Unit, Object and Subsidiary. D365 F&O replaces AAIs with posting profiles and requires that account key to be decomposed into a main account plus financial dimensions, which becomes the defining exercise of the whole programme.
Signature change
AAIs + Business Unit.Object.Subsidiary → Posting profiles + main account and financial dimensions