Question

What is the difference between

• A simple fields-accesors-mutators class
• A rich-modeled class

What constitutes rich modeling in business-domain classes?

Answer 1

‘Rich’ as used here implies ‘rich behavior’ (as opposed to state).

There is technical behavior and domain behavior. Accessors and mutators are technical; they lack the ‘why’ which defines business interest.

Domain objects represent the ‘why’ and encapsulate the ‘how’. Actually, all objects do that; domain objects do it specifically for business value.

Let’s say you, as an employee domain object, have to request a day off of work. You have 2 options:

1. Tell your manager and he marks the schedule.
2. Ask your manager for the schedule and mark it.

Model 1 is rich. The ‘why’ (vacation time) encapsulates the ‘how’ (marking the schedule).

Model 2 relegates the manager to a simple property bag and leaks the scheduling abstraction.