Final answer:
The domain model class diagram is principally used to represent the software classes related to the user's problem domain, by showing the data entities and their relationships, which are crucial in system design.
Step-by-step explanation:
The domain model class diagram is used to show the software classes in the user's problem domain. It is an essential part of software engineering that helps in designing systems by representing and detailing the system's data entities and the relationships among them. By identifying the classes that correlate with real-world objects or concepts, the domain model facilitates a bridge between the problem space and the software system. It does not typically show the things that are considered unimportant; instead, its focus is on identifying the relevant entities and modeling their interactions.
With a domain model class diagram, students can create representations and models of natural or man-made phenomena and systems in the domain. This tool is critical in understanding and communicating the requirements and structure of the new system before actual development begins.