What role do system attributes play in a class diagram?

System attributes in a class diagram serve to describe the properties of classes. These properties, also known as attributes, are essential characteristics that detail the state or data held by each class within the model. Attributes help in defining the specifics of how a class will behave and what kind of information it will store.

For instance, if you have a class that represents a "Student," the attributes might include "name," "age," and "student ID." This gives an immediate understanding of the type of data that the "Student" class handles. Having well-defined attributes is critical for ensuring that the class has the necessary data structures to function properly within the system.

In contrast, while user interactions pertain to how users interact with the system, they are not encapsulated within class attributes. Similarly, methods' access levels relate to permissions and visibility of class methods but do not describe the inherent properties of the class. Class relationships, although vital in a class diagram for showcasing how classes interact with one another, do not communicate the specific characteristics or traits of an individual class. Hence, attributes distinctly focus on the descriptive aspects of the class itself.