ConstantFieldSvc Node1 ConstantFieldSvc - m_fieldX - m_fieldY - m_fieldZ + ConstantFieldSvc() + ~ConstantFieldSvc() + initialize() # makeField() * m_fieldX * m_fieldY * m_fieldZ Node2 G4MagFieldSvcBase # m_fieldHolder + G4MagFieldSvcBase() + ~G4MagFieldSvcBase() + getField() # makeField() Node2->Node1 Node3 extends< AthService, IG4FieldSvc > Node3->Node2