A Domain Class is Class which presents aspects either
1-The Problem Domain Class
2-The Solution Domain Class
The Problem Domain Model: The Problem Domain Model is the set of classes attributes and relationships that describes the conceptual space of the System Under Development.
The PDM is used During Requirements Analysis to understand the types of information that the users of the sud must records or manipulate.
The solution Domain Model(SDM) :Is the set of classes ,attributes and relationship that must be coded to solve the requirements of the sud.
Typically one uses the Problem Domain Model as the starting point for the solution Domain model.
-->Domain classes Content "things I know"
-->Service classes Content "things I do"
Domain class are conceptual entities. They often related directly to things we talk about or use in the real world.
Service classes are strictly a component that exists only in the "solution" space; classes that you create in order to accomplish the goals of the SuD
