How might a frame actually work? Imagine a current state of affairs represented by a pronome agent, and another agent representing a frame. an AND-agent would link the two. "According to this simple scheme, a frame could consist of little more than a collection of AND-agents, one for each of the frame's pronome terminals." How would a frame learn which polynemes should fill its terminals? You could have a "virgin K-line" as the thing directly connected to the terminal; eventually the terminal would be connected to whatever the K-line learns.
NB: Crucial point here -- frames are not primitives, because they are built out of subcomponents!