Chapter 6. Application Domain Layer

The objects used by your application represent its domain. Unlike other database platforms where record data is, by default, hidden from end users, the Force.com platform displays record data through the standard Salesforce UI, reports, dashboards, and Salesforce1 mobile application. Surfacing the labels and relationships, you give your objects and fields directly to the end user. From the moment you create your first object, you start to define your application's domain, just as Salesforce Standard Objects represent the CRM application domain.

Martin Fowler's Patterns of Enterprise Application Architecture also recognizes this concept as a means of code encapsulation to combine the data expressed by each object with behaviors written in code that affect or interact with that data. This could be Apex Trigger code, providing defaulting and validation, or code awarding championship points to contestant records or checking rules compliance...