While modeling a data warehouse with an Analysis Services OLAP cube for a customer I ran into a problem with a "special" fact table. The customer wanted to do the following tasks with his cost controlling system:
1. Forecasting fulltime equivalents, head counts and costs of employees for the next 12 months on a monthly basis.
2. Displaying the forecast history on a daily granularity.
Full time equivalent (FTE) means the amount of work an employee can do. If he has a working capacity of 100% he does 1.0 FTE. If he only works the half day, he does only 0.5 FTE.
Head counts are simply the amount of employees the customer has, not regarding the working capacity.
And costs are monthly salaries and further costs paid for an employee.
Because forecasts are a fact to change, we should actualize the forecasts stored in the fact table. But regarding the second requirement, we cannot simply change or delete the records in our fact table, because if we do that, we will lose our history. So there ...