clarity of concept

> I was missing a word in my rant: why we need MANDATORY interfaces?

Please see my earlier post. All D-Bus objects can -- and in my experience, usually do -- implement methods and properties from multiple interfaces. Now it may be perfectly logical to have a "default" interface per object which handles unqualified names, but that seems like it's best just handled by your client library. If your client library doesn't make this easy for you, use a different one.

Anyway, this discussion is pretty moot. The D-Bus specification [1] has been around for over a decade, and although it may have its warts it works well enough most of the time. You can argue that it's wrong, but it's not going to change the fact that it already exists.

[1] http://dbus.freedesktop.org/doc/dbus-specification.html