for G1, G2 being _Graph
for F being PGraphMapping of G1,G2
for v being Vertex of G1 st F is onto & F is semi-Dcontinuous & v in dom (F _V) holds
( ((F _V) /. v) .inDegree() c= v .inDegree() & ((F _V) /. v) .outDegree() c= v .outDegree() )