These measures usually have the following characteristics:

• They are numerical
• They can be aggregated (summed up or operated in some way)

The Facts usually map directly to one or more columns in a Fact table. The Fact is defined with a MicroStrategy expression. An expression could be:

• Base: an expression which is represented as a single table field
• Derived: an expression in which two or more table fields are operated or a function is applied to them

The Fact on its own is meaningless. It needs a context and a rule of aggregation in order to be useful. In the following sections, we will learn about which other MicroStrategy Objects serve this purpose.