Cocoa data hierarchy and browser

Question

I am trying to implement something similar to the iTunes browser, to the browser of a simple book database. I have the following objects - Author , Genre and Book . I would like to display a list of authors and a list of genres that act to filter the main list of books.
I tried to do this in two different ways: modeling:

Author ( has many ) Genres ( has many ) Books

... with several instances of the same genre, so each author has his own name for a particular genre, I have a good drilling hierarchy displayed in my tabular views (albeit a little illogical to duplicate genres). However, when I select several authors, I finish showing the hype of the same genre, because they are, in fact, separate objects.

So, I tried to do this, more intelligently, with this relationship:

Author ( has many ) Books  
Book ( has one ) Genre

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Answer 1

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UPDATE
:

• "bookFilterPredicate" .
• Author Genre.
• selectedObjects .
• : self.bookFilterPredicate = [NSPredicate predicateWithFormat:@"author IN %@ && genre IN %@",authorArrayController.selectedObjects,genreArrayController.selectedObjects];