So let's put in both "localized" and "translated".  If a given item has neither a localized nor a translated tag, it is not derived from any other content.  If it has only localized, it is both localized and translated from that item.  If item X has translated of Y and localized of Z, we could enforce the rule that Y must be in a translation chain leading to Z, or we would could just not bother.  Should it be allowable to have a "translated" but not a "localized"?