Debugging forall/3

Hi,

I just see (p(a), q(a), q(b) in the database):

| ?- forall(p(a),q(a)).
       1    1  Call: forall(p(a),q(a)) ?
       2    2  Call: p(a) ?
       2    2  Exit: p(a) ?
       3    2  Call: '$not'(q(a),forall,2) ?
       4    3  Call: q(a) ?
       4    3  Exit: q(a) ?
       3    2  Fail: '$not'(q(a),forall,2) ?
       1    1  Exit: forall(p(a),q(a)) ?

(1 ms) yes

Is the display of the '$not' intended? How about
the '$not' surrounding the p/1 call?

Bye