Measure: Additive, Semi-additive and non-additive

Measures are the values in your fact tables which provide numeric meaning to the business process event. There are three kinds of numeric measures.

1 (Fully) Additive

They are the measures that can be summed across any dimensions associated to the fact table. Sales Amount, Quantity Sold are the example. You may sum the sales amount across different dimensions to get the monthly sales amount, store sales amount and product sales amount. 

2 Semi-additive

They are the measures that can be summed only in some of the dimensions associated to the fact table. Account Balance and Quantity Stock On-hand are the example. You may sum the Account Balance across customers to get the Branch Account Balance. But you can't sum the Account Balance across dates. Similarly, you may sum the Quantity Stock On-hand across product to get the Store Quantity Stock On-hand. But you can't sum it across dates.

3 Non-additive

They are the measures that can not be summed in any dimensions. They include the unit values (e.g. unit cost/price), values of intensity (e.g. temperature) and values in percentage or ratio.

We highly recommend using the additive measures if possible. So, we usually don't store the measures in the form of percentage / ratio. But break it down to additive measures which are their original numerator and denominator. For example, we won't store the measure "Unit Per Transaction (UPT)" directly but save in two measures, Unit Sold and Transaction Count.