SQL translation into Relational Algebra NOT IN

Question

I have the Uni-Schema which can be found here http://hyper-db.com/interface.html#

i try to translate the following SQL Code into Relational Algebra

select distinct s.*, h.vorlnr
from studenten s inner join hoeren h on s.matrnr = h.matrnr
    where h.vorlnr not in (select v.vorgaenger from voraussetzen v)

my try is :

π_s.*(
           p_s(studenten) ⋈_{s.matrnr=h.matrnr} p_h(hoeren)
                     ⋈ _{h.vorlnr=v.vorgaenger} p_v(π_{v1.vorgaenger}(
                           voraussetzen - σ_{h1.vorlnr!=v1.vorgaenger}(p_v1(voraussetzen) x p_h1(hoeren))))

is that right ? if not why ?

Answer 1

yes it is right (y) because it is right