The schema in Figure 16.3 is composed of a central table (Sale) linked by foreign
key connections to outer tables (Item, Store, and TimeDimension). This is called a star
schema, since the central table may be viewed as the center of a star pattern, with its
outer tables becoming “points of the star”. In data warehousing terminology, the central
table is called a “fact table” and the outer tables are dimension tables. Since all
tables contain facts, the term “fact table” is rather inappropriate here. Moreover, ORM
uses the term “fact table” to mean an atomic fact table. To avoid confusion, we’ll use
the more descriptive “central table” instead of the more popular “fact table” in this
context.