I've been pondering the best way to show a deep hierarchy for a desktop application I'm working on. Here are some alternative designs I'm considering...

**Mac OSX Finder:**

![alt text](https://ptgmedia.pearsoncmg.com/images/chap03_9780789742292/elementLinks/03fig06.jpg)

If you understand what you're seeing, the "Columns View" does a great job of showing context (where am I in this giant hierarchy?), and you can browse quickly through lists of folders to see what's in them...but it sure uses some screen real estate.

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**Microsoft's MSDN Navigator**:

![alt text](https://i.stack.imgur.com/pGRA7.png)

Basically, what's going on here is that you can see the "parents" of the page you're looking at, and you can see any "children". You give up on seeing the "siblings" at the different levels, but that saves you a bunch of screen space. So, you give up some context in exchange for compactness.

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**Windows Navigator:**

![alt text](https://i.stack.imgur.com/nB9Qy.png)

This UI is decent at showing context right up until the point that you have to start vertically or horizontally scrolling. If you have lots of items and lots of levels, you'll be scrolling a lot. That said, you can pop open multiple folder branches at a time. This provides a sort of mini-history (what folders have I popped open so far?).

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**"Mega-Menus":**

![alt text](https://i.stack.imgur.com/0f1Nz.jpg)

In this example, you're looking at about three levels of the hierarchy. If you're clever, I imagine you could show maybe a fourth of fifth level, but at some point, it's going to either break down or devolve into something more traditional (tree view, etc.).

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**Questions**

Obviously, no one can answer for me which type of hierarchy UI I need unless you understand the task I'm trying to support, but I do have some specific questions:

1. **How prevalent are each of these alternatives?** I haven't been a Mac user for a long time, and I really haven't seen a UI like the Finder's Columns View anywhere besides on a Mac. Does it exist anywhere else? Would you use it on a non-Mac interface? The "Mega-Menus", conversely, seem very prevalent. I see the tree-view (as in Windows Explorer) all over the place (in Windows apps, on the web, etc.). It's basically a standard GUI widget. I haven't seen the MSDN navigator anywhere else but on the MSDN site.
2. **Do users "get" these interfaces?** This is probably highly correlated with the prevalence question, but if I put, say, the Columns View in front of non-Mac users, would they be completely stumped? Any data or experience with this? I would be very wary of using that MSDN one unless I had some data to prove that non-programmers would understand it.
3. **Am I missing any alternatives?** What other hierarchy UI's or variations on these have you seen?