behaviour of ASK-based validators

This part of the description of the behaviour of ASK-based validators doesn't
make any sense at all.  I have no idea what is supposed to be going on here.

"Let QS be the union of the solutions produced for each value node v in vs
so that the solution variable this is bound to the focus node and value is
bound to v."

Peter F. Patel-Schneider
Nuance Communications