On the basis of relations between the national government and its constituent parts, such as states or provinces, the government can be classified into unitary and federal. In a unitary government, the relationship between the centre and its constituent parts such as states or provinces are largely one-sided, with the central government enjoying almost complete control over its constituent parts such as states or provinces. In a unitary system, almost all power and responsibility are vested in the central government. Local governments may only exercise power through the central government. In this system, sovereignty is vested in the central government alone.