01Interactive object models
A 3D model that knows how it works: which parts move, on what hinge, how far, how heavy, what it collides with, and how it breaks. Found from the model alone, checked in a physics simulator, shipped as a standard file with an open description beside it.
02Interactive world models
A world that knows what happens next: when a door is pushed, a car is driven, or a vase is dropped, the scene answers back the way the real one would. The objects above are the first thing such a world is made of.
03The frontier between the two
Things in places, both running live in an engine. A player needs a door to open; a robot needs a door it can learn to open. Both need the hinge in the right place, and both need it to cost an upload, not a team.