Business Transaction Events (BTE)

There are 2 types of BTE:
(1)   Publish & Subscribe interfaces: These interfaces inform external software that certain
events have taken place in an SAP standard  application and provide them with the data
produced. The external software cannot return any data to the R/3 System.
(2)    Process interfaces:  These interfaces are used to control a business process
differently than the way in which it is handled in the standard R/3 System. They intervene in
the standard process, and return data to the SAP application.
    -> Publish & Subscribe interfaces:
.  Allow you to start one or more (multiple) additional operations when a particular event
    is  triggered. They do not influence the standard R/3 program in any way.
. Multiple operations do not interfere with each other.
. Add-on components can only import data.
. Possible uses: Additional checks (authorizations, existing duplicates, and so on)
-> Process interfaces:
. In contrast to Publish & Subscribe interfaces, data exchange takes place in both directions
with process interfaces. This influences the number of additions that can be attached to the
interface.
. When an event is triggered, a process in the standard program can only be replaced by a
single external process using the process interface.
. If you are using an add on from an SAP partner that uses a process interface, this
enhancement is processed at runtime. If you choose to use this same process interface for
one of your own developments, the partner enhancement is dismissed and your own
enhancement is processed at runtime instead.

Finding Business Transaction Events :
SAP Reference IMG -> Financial Accounting -> Financial Accounting Global Settings -> Business Transaction Events
? For Publish and Subscribe Interfaces, Environment - > Info system (P/S)
? For Process Interfaces, Environment -> Infosystem(Processes)
- Find for Character String "OPEN_FI_PERFORM" in source code