What are the four primary functions of a corporate-level strategy within a multi-business company?

In a multi-business company,strategic management encompasses four major tasks at the corporate
level: 1.Providing a clear overall vision for the single business units,exercising guidance and control over the individual businesses; 2.Allocating resources to the single business units,thus managing the portfolio in a way that cash flow and risks are balanced,and sustainable long-term growth is achieved; 3.Managing linkages among the business units and exploiting synergies; and 4.Developing central competence and providing services and resources to the business units.