The structure of facts

As shown in the diagram below, facts are made up of the following components:

The fact definition is composed of one or more fact expressions. Every fact must have at least one expression. Fact definitions are discussed in detail in How facts are defined .
The column alias stores the column name MicroStrategy uses to generate SQL statements when creating temporary tables related to the fact. Every fact must have a column alias. MicroStrategy selects a default column alias depending on the type of fact, unless you create a new column alias. Column aliases are discussed in detail in Fact column names and data types: Column aliases.
Fact level extensions allow facts stored in the data warehouse at one level to be reported at an unrelated level. Extensions can also prevent a fact from being reported at a certain level, even though it is stored at that level. Level extensions are very effective for advanced data modeling scenarios. Level extensions are discussed in detail in Modifying the levels at which facts are reported: Level extensions.

You create facts in MicroStrategy Developer using the Fact Creation Wizard and the Fact Editor. During project creation with the Fact Creation Wizard, when you select the numeric column used to represent the fact, both the fact definition and column alias are automatically defined. Level extensions are optional.

For a discussion of the tools used to created facts and procedures on how to use them, see Creating facts.