A man wearing a headset is giving a presentation.
The presentation is about a product.
Not all presentation is about a product it could be any type of other presentation.
exists e1 e2 x1 x2 x3 x4.(Theme(e2,x4) & Actor(e2,x1) & v_give(e2) & n_presentation(x4) & Theme(e1,x3) & Actor(e1,x2) & v_wear(e1) & n_headset(x3) & (x1 = x2) & n_man(x1))
exists p1 x1.(n_presentation(x1) & exists x2.(about(x1,x2) & n_product(x2)))