It is important to consider the nature of the facts you are defining in order to avoid sources of error. Discover the different types of facts below.
The different additivity properties of fact tables
When choosing facts, it is important to examine their additivity properties:
Additive facts
An additive fact can be added in any dimension.
Example: a turnover figure.
Sem-additive facts
A semi-additive fact cannot be added in certain dimensions.
Example: the number of parcels left to be delivered at a given moment is not temporally additive, but it is spatially additive.
Non-additive facts
A non-additive fact can never be added.
The only possible action is to calculate counts or averages. Example: the unit price of a product.
Conformed facts
A fact is said to be conformed if it exists in different fact tables under the same name, and when the definitions and underlying calculation methods are the same. @Kimball2003