G4UA::StepHistogramTool Node1 G4UA::StepHistogramTool - m_config - m_histSvc + StepHistogramTool() + initialize() + finalize() # makeAndFillAction() - BookHistograms() Node2 G4UA::UserActionToolBase < StepHistogram > # m_actions + UserActionToolBase() + fillUserAction() # makeAndFillAction() Node2->Node1 Node3 extends< AthAlgTool, IUserActionTool > Node3->Node2