Implementing Delta Import in a custom (ECMA2) management agent

I'm implementing a custom management agent, and I was wondering what I'm actually supposed to return during a Delta Import operation.

Am I supposed to return:

1) All the changes that were performed on the connected system since the previous import operation, including those coming from exports

or

2) Only the changes that happened in the connected system independently of the export operations that were performed?

An example: suppose that in the connected system I have users A and B.
We run a full import.
After that, the displayName of A is changed in FIM, and consequently A is modified during an export.
B is not modified in FIM, but a system attribute which I'm importing changes in the connected system.
At the next delta import, should my MA return only B or both A and B?

This is an ECMA2 MA, but I think the principle should be the same for ECMA1.

Thanks,
Paolo

Paolo Tedesco - http://cern.ch/idm