A Flow tag can be assigned to Accounts dimension members bearing formulas.
The following example describes the problem to be solved with flow metrics. Assume you have Sales and Additions figures for all 12 months. You want to perform an aggregation to populate each month’s beginning inventory.
You would use an MDX formula on the Beginning Inventory member in order to calculate its value. Without flow metrics, to obtain each month’s beginning inventory, the calculator engine would have to reiterate the MDX formula exponentially.
Inventory = SUM(MemberRange(Jan:Time.CurrentMember), (Additions - Sales)) + Beg_Inventory
To optimize the illustrated example, assign the Inventory member the formula (Addition – Sales), and tag the member as Flow.