Domains

A domain is a pool of values used to populate specific columns in data records. These columns are said to be based on the domain. Each column known to USoft Definer must be based on exactly one domain.

'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.

To define a domain:

1.	Choose Define, Domains from the USoft Definer main menu.

The Domains window or tab opens.

TIP: If you are new to domains, you may prefer to use the New Domain Wizard. Bring the catalog into view in the left of your screen (choose View, Catalog from the main menu). Click on the Model and Rules tab, then double-click on Domains. This will open the New Domain Wizard.

2.	Type an appropriate Domain Name, for example, AREA_CODE.

3.	Set Data Type, Column Width and Display Type. Column Width is not needed for large data objects such as CLOB, BLOB or NCLOB.

4.	Depending on what your domain is for, you will now want to set further attributes:

•Allowed values.

•Default values.

•IO Formats

•Unique values.

•A superdomain.

5.	Save work.