Accumulating Fact Table

An accumulating fact table is where all of the dimensional attributes are not available at the time of creation and the dimensions that are linked to a fact table change over time. The most common implementation of this is in the recording of dates against facts. 

Take a "Sales" fact, typical dates you may be intersted in when tracking an individual sale is maybe, order_date, ship_date, delivery_date and payment_date. These would not all be available when the fact is first created. Over time the fact record would accumulatemore relationships with the dimensions as the relevant date milestones were passed for the sale.