Scope of interop

Dear all, also during yesterday's call we started to talk about the
scope of the interop. By scope we meant on what protocols (i.e., core
and profiles) we would like to define test cases and conduct interop
tests, and for each of those profiles and/or core, what features we
would like to target.

Could we start a thread of discussion on this topic?

Here it comes my initial contribution, restricted to the core :

Core: I think that we should define test cases for the core. As for
features see below:
Type of input documents: