BOR (Business Object Repository) was used until ES Version 8.3 to develop business objects(BOD's). From Version 8.3 on wards, Integration Studio and Business Studio are being used. Latest being LN Studio.
BOL(Business Object Layer) - It is a set of standard DLL's which are available during run time. They invoke the business logic methods in order to handle the BOD functionality.
BOR is just a repository and serves as a virtual space in BOD.
BOI(Business Object Interface) and BDE(Business Data Entity) serves almost the same functionality i.e. providing a way to BaaN/LN a way to interact with external world using SOAP based architecture involving web-services.
BOI was being used until Baan IV/5 while BDE's are used with LN.
More more details on each, go through the standard documentations provided by Infor. There is always more to it.
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