Several people are participating in an athletics class.
A group of people are practicing yoga indoors
Not all athletics classes are yoga and not all athletic classes are indoors.
exists e1 s1 x1 x2 x3.(in(e1,x2) & n_class(x2) & of(x2,x3) & n_athletics(x3) & Actor(e1,x1) & v_participate(e1) & n_people(x1) & a_several(s1) & Theme(s1,x1))
exists e1 x1 x2 x3 x4.(Theme(e1,x3) & Actor(e1,x1) & v_practice(e1) & n_indoor(x3) & of(x3,x4) & n_yoga(x4) & of(x1,x2) & n_people(x2) & n_group(x1))