Corporate level strategy vs Business Level Strategy

The Kaplan text, which is largely based on the JWS book, argues that CORPORATE level strategy includes diversity of products/ services or business units.

However, mean time, the JWS book also agrues that business level strategy is also concerned with which products or services should be developed in which markets.

My question is should choice of products or markets be a corporate level or business level strategy?

Besides, the Kaplan text also argues that corporate level strategy is conerned with leaving and entering the industry. However, in its illustration, it says should another range of shops opened to target at different segment of market is also a corporate level strategy.

Can I say any thing up to (including) segmentation is a corporate level strategy? Coporate level strategy is not just about choosing market?

I find different books categorise segmentation/product choice/product range/product development either under corporate or business level. Do they really know what they are talking about?