The Tower of UI Design comes from Ryan Singer. It looks like this:

  • Domain: Life experience.
  • Situation: What's happening "at 2pm on a Tuesday"?
  • Flows: Walkways through the app; chains of affordances
  • Affordances: Connect the screens of a given flow.
  • 2D Layout: The arrangement of elements on a given screen. "How it looks".

Time and Space

The first 3 from the top (domain, situation, flows) involve the element of time. The last 2 are focused on "space".