digraph G {
 rankdir=TB
 node [shape=box, fontsize=9, height=0.1, width=0.05 ]
 edge [arrowsize=0.5, len=0.1]
"HelloSystem\n"->"GreetingConcept\nSalutationConcept\nuser_message\n"
"GreetingConcept\nSalutationConcept\nuser_message\n"->"GreetingConcept\n"
"GreetingConcept\nSalutationConcept\nuser_message\n"->"SalutationConcept\n"
"GreetingConcept\nSalutationConcept\nuser_message\n"->"user_message\n"
}