let G1, G2 be _Graph; :: thesis: for F being PGraphMapping of G1,G2
for e being object st e in dom (F _E) holds
( (the_Source_of G1) . e in dom (F _V) & (the_Target_of G1) . e in dom (F _V) )
let F be PGraphMapping of G1,G2; :: thesis: for e being object st e in dom (F _E) holds
( (the_Source_of G1) . e in dom (F _V) & (the_Target_of G1) . e in dom (F _V) )
let e be object ; :: thesis: ( e in dom (F _E) implies ( (the_Source_of G1) . e in dom (F _V) & (the_Target_of G1) . e in dom (F _V) ) )
assume A1: e in dom (F _E) ; :: thesis: ( (the_Source_of G1) . e in dom (F _V) & (the_Target_of G1) . e in dom (F _V) )
consider f, g being Function such that
A2: F = [f,g] and
( dom f c= the_Vertices_of G1 & rng f c= the_Vertices_of G2 & dom g c= the_Edges_of G1 & rng g c= the_Edges_of G2 ) and
A3: for e being object st e in dom g holds
( (the_Source_of G1) . e in dom f & (the_Target_of G1) . e in dom f ) and
for e, v, w being object st e in dom g & v in dom f & w in dom f & e Joins v,w,G1 holds
g . e Joins f . v,f . w,G2 by Def8;
thus ( (the_Source_of G1) . e in dom (F _V) & (the_Target_of G1) . e in dom (F _V) ) by A1, A2, A3; :: thesis: verum