What is the difference between business strategy and corporate strategy?

What is the difference between business strategy and corporate strategy?
A business strategy deals with the direction a particular SBU (Strategic Business Unit) aught to move. This SBU along with other SBU's will be given resources to implement their strategy by the parent group, this parent group is the select few e.g. the CEO, CFO, President, and other corporate elite who collectively decide the corporate strategy.
For example, Steve Jobs of Apple will decide the corporate strategy of his companies SBU's by deciding which area should receive the most attention. From this, the heads of these SBU's which range from computers, phones, to MP3 players, will then decide the business strategy for each product, they will have complete authority within their own unit (own product) while those involved in corporate strategy have authority over all business units.