Right now I'm using two lists side by side where clicking on an item in list A filters list B to offer only the Bs related to the selected A, and Vice Versa. So clicking on B3 make A2 and A5 disappear so you know that B3 is related to A1, A3 and A4. I believe the mental model is not strong enough to make it instinctive to use so I have to provide all sorts of icons and animations to make it convincing. It doesn't help that other stuff is happening at the same time, like details appearing under a selected item and the such. I was hoping to achieve a stronger mental model by providing a metaphor to the user.

The Parents/Children, metaphor seems good, but it only really allows for exactly 2 parents for every child. And if you forget the biological aspect, you end up with the Tree metaphor of Parent/Children where each child has exactly 1 immediate parent (not many-to-many).

Books/Authors are better, but books are usually seen on shelves, which reduces the metaphor to a list.

I'm looking for a metaphor where you can have a shelf full of books AND a room full of authors at-the-same-time, hence the idea to 2 lists. Or a mutation which allows humans to conceive three-way-babies. I think the need for a better metaphor is evident.

Are there other options out there to illustrate many-to-many relationships?

Edit: In particular, I'm looking for a metaphor which will allow easy exploration of both kinds of elements in one metaphor. For Books/Authors, I need a bookshelf and a room full of authors: two metaphors. For Students/Classes, I need a list of students and a list of classes: How can I make it as easy to look through the students as it is to look through the classes?

  • 1
    A social network of friends... or teacher <-> child, student <-> class, library book <-> borrowers? Nov 29, 2011 at 9:39
  • How do these solve the Books/Authors problem?
    – Shawn
    Nov 29, 2011 at 19:08

3 Answers 3


Elastic Lists are my preferred UX pattern for handling this situation. Here's a great example.


  • Great example indeed. This gives a couple of ideas!
    – Shawn
    Nov 30, 2011 at 4:07
  • and it's visually appealing
    – akousmata
    May 14, 2015 at 13:19

What about cars/motorcycles?

A manufacturer builds cars/motorcycles and a car/motorcycle can be built by several manufacturers.

  • BMW >-< car >-< Porsche
  • BMW >-< motorcycle >-< Ducati

You could also do this for any product, perhaps picking a product geared at your user base would suffice.

  • Sony >-< TV >-< Samsung
  • Nike >-< shoe >-< New Balance
  • These are good metaphors, but they suffer from the same problem as Books/Authors. I'm looking for a metaphor which will allow easy exploration of the many-to-many relationship.
    – Shawn
    Nov 29, 2011 at 18:59
  • @Shawn I'm a bit confused by what you're needing. In your edit it seems as though you are content with the "A bookshelf and a room full of authors" metaphor. Are you looking for something along those lines with another metaphor? Nov 29, 2011 at 21:02

The best thing that comes to mind is Movies & Actors … (more specifically movie credits & actors' résumés). Every movie has credits made up of actors, and every actor has a résumé made up of movies.

While this is very close to books and authors, most everyone is familiar with either IMDB (Internet Movie Database) or the Six Degrees of Kevin Bacon, so it's easier to identify with.

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