Hi,
There are no Dimension tables but still there is one dimension table called Package Dimensions - it contains Data Package, Unit and Time dimensions.
As Benedict already mentioned in In Memory Infocube, Fact table has SIDs - that are directly mapped to master data.
Infocube is now a Star Schema - earlier it was extended star schema
In Memory Infocube has made modeling simpler as now there are no aggregates, partitioning, indexes.
2) If thats the case, why was info cube built at all.
One of the reason is:
-non-cumulative keyfigures can only be modeled in InfoCubes,
-integrated planning can only be done on (transactional) InfoCubes,
-the external write-interface (RSDRI) only works for InfoCubes .
Similarl you can find many other reasons
For more reference, check the below links: