:: deftheorem Def3 defines Theta WAYBEL29:def 3 :
for X, Y being non empty TopSpace
for b₃ being Function of (InclPoset the topology of [:X,Y:]),(ContMaps (X,(Sigma (InclPoset the topology of Y)))) holds
( b₃ = Theta (X,Y) iff for W being open Subset of [:X,Y:] holds b₃ . W = (W, the carrier of X) *graph );