abstract Node

abstract Edge ->> Node *

weight -> integer

[ this > 0 ]

total_weight -> integer = sum Edge.weight

N1 : Node

E1 : Edge -> N2 ?

[ weight = 1 ]

E2 : Edge -> N2 ?

[ weight = 2 ]

E3 : Edge -> N3 ?

[ weight = 5 ]

N2 : Node

E4 : Edge -> N3 ?

[ weight = 2 ]

N3 : Node

E5 : Edge -> N4 ?

[ weight = 1 ]

N4 : Node