An author name is the name of an agent used to identify it as an author. It is not necessarily unique; authors may go by pseudonyms. A particular author.name of an author must be either the author's real name (i.e., her agent.name), or else it is one of her pennames.
(=> (Author.Name ?Author ?Name) (Or (Agent.Name ?Author ?Name) (Penname ?Author ?Name)))