BPM - Message Interface

Hello all,

I have some doubts about Messages Interface used in BPM.

BPM just used Abstract Message Interfaces, but to expose the Interface to sender aplication, XI need the same Message Interfaces that is declared abstract but no abstract.

My question is how the Business Process Engine that the Outbound Message Interface, that my application is using, is the Abstract Interface that activate my Integration Process???

Regards,

Luiz