Can you tell me whether I'm understanding this correctly?
Would this query result in, e.g. [(director: Null, author: J.K Rowling), (director: Spielberg, Null), ...] or would it be [author: J.K. Rowling, director: Spielberg, ...] or just plain strings: [J.K. Rowling, Spielberg, ...]? I still don't totally get the model here.