>it seems to me, one would always design for flexibilty (t2) Clearly not - the OLAP field exists and brings in untold billions of dollars, so there is no short

>it seems to me, one would always design for flexibilty (t2) Clearly not - the OLAP field exists and brings in untold billions of dollars, so there is no shortage of takers. OLAP design is about finding an optimal point between two extremes: 1. put effort to pre-compute everything, gain a lot of speed while looking at the result. 2. don't pre-compute anything, spend more time waiting to visualize the result. If things are fast enough for you in the extreme #2 then you don't need to precompute everything and you can enjoy the flexibility. But for many people this is not the case - they either want results in split-second (highly interactive systems, modeling with varying parameters over an over again), or they want to dramatically increase amount of data (e.g. not just all sales but also all page views).