Software is a behavior, not a sequence.

Good interface work still asks what does the user see, understand, and touch. Behavior design adds the question underneath it: what does the system do, when, on whose behalf, with what confidence, and how does it tell the truth about that. These questions have a history in interaction design and mixed-initiative systems; generative software increases their reach. The unit of design is not only the screen. It is the negotiation the screen makes legible.