In Archimate you have a application function depited in ARIS as a IT function type and in BPMN you have the following activity types that represent application functions: Service task, Scrip task & Transactions, but they are depicted as function types in ARIS. The impact is that it is not possible to reuse BPMN activities (function type) on Archimate models as application functions as they are (IT function types). Is this correct or is there a flaw in the way that ARIS supports it?
In my opinion, we model the smaller activities (OTOPOP, like EPC) in BPMN, whereas the application function in ArichMate is an IT function that resides on a higher level of detail, not showing the same amount of detail, such like a Level 2 Value Added Chain Diagram.
For example, the IT Function could be "Bill Processing - Online" where lower level activities would be, for example, a BPMN model which is named "Process Bill for Online Purchases" which is modeled with multiple functions such as
Validate customer data
Confirm complete order
Create Merchant sales statement
Send Merchant sales statement
Receive Merchant sales confirmation
Send product transfer approval
However, you are right that the Script or Service task could also be linked in the lower levels, have you tried to create assignments instead?