'Domain' is one of the fundamental concepts of the USoft Definer model. Perhaps the primary purpose of a domain is to communicate to the RDBMS what is the desired datatype and data length of each column. In this capacity, a USoft domain is the equivalent of 'NUMBER( 8, 2 )' or 'VARCHAR( 256 )' clauses in traditional CREATE TABLE or ALTER TABLE statements.
But USoft domains serve many more purposes. They allow you to:
•Build a highly consistent data model by inviting you to re-use, where possible, column characteristics for like columns across your entire model.
•Check that only allowed values are admitted to the database.
•Handle default values and predefined data formats. Dates and times are examples of data where predefined data formats are important.
•Generate unique values that can act as a handle for identifying individual data records.