The positions are continuous functions of time. Energy is conserved. Momentum is conserved. Angular momentum is conserved.
Momentum transfer is perpendicular to the plane of contact.
The two objects do not interpenetrate. Sometimes the frame axiom is the same as the causal axioms. It is this kind of consideration, I think, that lies behind Ken's feeling that a richer domain theory would avoid the frame problem by adding more axioms. The point is that the person building a theory or program will generally have to consider frame inferences as an intrinsic part of the theory of change in the domain, and that the theory or program will have to explicitly deal with them. After that, there's no need for non-monotonic inference.