In order for complete accuracy to be assured, the granularity of time for the capture of changes in the dimensions must be the same as the granularity of time for the capture of the measurable fact events. In practice, this is hardly ever possible. There is an inevitable delay in time between the change event and the capture of that change in the source system. There is, usually, a further delay between the implementation of the change in the source system and the subsequent capture of the change in the data warehouse.
The challenge for data warehouse designers is to minimize the delays in the capture of changes.
In order for complete accuracy to be assured, the granularity of time for the capture of changes in the dimensions must be the same as the granularity of time for the capture of the measurable fact events. In practice, this is hardly ever possible. There is an inevitable delay in time between the change event and the capture of that change in the source system. There is, usually, a further delay between the implementation of the change in the source system and the subsequent capture of the change in the data warehouse.
The challenge for data warehouse designers is to minimize the delays in the capture of changes.