<Transmittal Root>
Every transmittal contains exactly 1 instance of <Transmittal Root> as the 'root object' of the transmittal — the root of the object tree.
Every object in a transmittal is connected by a path of aggregate/component relationships with the <Transmittal Root> of that transmittal.
Consequently, a <Transmittal Root> serves as the ultimate organizer of organizers for a transmittal.