I did state that you would implement the ihydratable in both info classes.

You would still use the ihydratablen interface for the BookInfo class and the AuthorInfo class.In your Bookinfo fill method you would only be mapping the basic bookinfo

If you were going to have a collection of bookinfo objects in your authorinfo class then you could loop through the authors collection and populate their books but you don't need to.

That's why I said you can even just leave out the Authors collection in the bookinfo object

Just grab the related authors when you grab the bookinfo or vice versa the related books when you grab an author.

(One note, in your original post you had arrays of firstname() and lastname(). this wouldn't work well because you are assuming they would match up firstname(1) goes with lastname(1). Your code could handle that but just a source of possible error.)

Hope this all makes some sense.