In process of building a new datawarehouse it is crucial to survey the current needs so solution can satisfy the actual and upcoming business needs - or at least majority of them.
From the source systems correct data has to be optimaly extracted with filtering duplicated and incorrect data.
However, often an in-memory solution better fits better than a data cube setup with complete datawarehouse process.
Design datawarehouse, survey users
Extract, transform and load data, handle historic data