top-down or bottom-up is a classic question with many potential contexts.
how do you model your company? without question, bottom-up.
how do you view economic policy? already the answer gets more gray and depends on personal feelings. which way you lean will direct your answer.
how do you display a feed? this question doesn’t seem to have a definitive answer and it’s the one that got me diving into this no mans’ land of product philosophy.
i have to bash twitter from time to time because it sucks at so many things (their persistent notifications problem befuddles me). yet, twitter is still one of the first places to go to see “how did they do it”? and twitter is the epitome of the top-down or bottom-up question.
the twitter new feed is top-down -- with the most recent posts at the top. yet in the very same app, they use bottom-up for direct messages -- with the most recent messages at the bottom.
whenever using any product, i love to ask the question of “why did they do this?” and i find that the answer usually falls into one of two buckets:
genius product insights from amazing design, ux, and customer involvement
copying someone else
the problem with copying is that while you know it works (at least you hope it works since at least one other idiot did the same thing), you also have no idea into the why. you don’t know if that was done for legitimate, customer-centric reasons -- or simply because that company shipped it that way for whatever reason, or lack thereof.
after going through my phone, the one trend i can see that determines top-down or bottom-up is what i’ll call “purposeful interaction”.
if the product is simply displaying new content that you’ve (implicitly) subscribed to or followed, then it just flows on top… examples being:
twitter (news feed)
if the product is more like a dialog, then every new message goes to the bottom… examples being:
looking at these examples, it does make sense for purposeful interactions to be bottom-up -- because you want to see the last message you're replying to when your keyboard pulls up.
of course, there are products that are starting to evolve beyond a simple top-down or bottom-up. facebook is top-down, albeit highly filtered and algorithm-laden. but then there’s examples like disqus, quora, or reddit which try to elevate the best content to the top -- whether that data is two seconds or two years old.