The idea is that you can construct scenarios based on information you're interested in and see how it affects everything else in the system. The data that you're using as a what-if scenario supersedes any "real" underlying data so that you can see what effect it has on everything else. A data lens.
For example, what effect would it have on ROI if the local market is trending up or down? What if the property had an additional 1000 square feet? What effect would it have had on your metrics for the last year if you had routed traffic differently?
This is a very heavy question to answer though because, once again, it requires that you calculate everything in advance, but not only for the original scenario but for every other scenario you're watching as well.
Another score for big data columnar data stores IMO.
