Remodeling (why it is different)

I know with the remodeling concept in NW04s (BI 7.0), we can add / delete/ replace fields (Characteristics / Key Figures) to an Infocube.

How it is possible to add or delete an infoObject from a Cube, even when it has data? Isn't it true that according to database concept, we would not be able to modify a table with data in it?