Each registration has an owner. When, for example, a name is changed, the old name and the new name have the same owner. This also permits one to distinguish among multiple uses of the same name (serially or simultaneously; both have occurred).
The date and kingdom attributes are all optional, although it is good to have them. Some items in the database are missing one or more of these.
Africa asks: It isn't entirely clear in the presentation which links between tables are one to many or many to many relationships, so perhaps this is already in mind or otherwise dealt with, but don't some registrations (such as household names) have more than one ("an") owner?
Herveus replies: In this schema, each registration maps to a single owner. Jointly held items would have a second registration for the joint owner (with a registration to registration link to the original registration) and a usage for the name or armory of "joint owner".