The idea behind a domain is that you create a single definition that is used in a number of different places. For example, you can define a single PFIELD object called Address and use this field definition in a number of different tables, or even many times in the same table. Each use of the field definition is a field assignment. This assignment establishes a field in the table with name and order specified in the assignment. This can be advantageous when you need to change some attribute of the field definition. You can make the change in a single place, and Roundtable makes sure that all of the tables that use the field definition are updated properly. This ensures consistency in your application and reduces the time spent on database maintenance.