A seamstress who had a surprise visitor at work.
A person was visited while they were working.
The individual had a visitor while at work, but that does not necessarily mean they were working.
exists e1 x1 x2 x3 x4 x5.(a_topic(x1) & at(e1,x5) & n_work(x5) & Theme(e1,x3) & Actor(e1,x2) & v_have(e1) & n_visitor(x3) & of(x3,x4) & n_surprise(x4) & (x1 = x2) & n_seamstress(x1))
exists e1 p1 x1.(exists e2.(Actor(e2,x1) & v_work(e2)) & n_thing(x1) & while(e1,p1) & Theme(e1,x1) & v_visit(e1) & n_person(x1))