Domain Object

A Domain Object is an object that represents concepts from the real-world domain targeted by a software system, encapsulating business logic and conceptual structure.

It serves as a central building block of the domain model, encompassing elements such as entities, value objects, services, rules, and events.

Domain objects are not just data structures or processing units within the system, but parts of a model that reflect the semantics and behavior of the problem domain.

SimpleModeling may use Domain Object as an umbrella term for both Classifiers appearing in a Domain Model and their Instances. When an explanation must distinguish design-time structure from runtime subjects, it explicitly distinguishes a Domain Classifier from a Domain Object Instance.

The umbrella term Domain Object must not be interpreted as making a Classifier and an Instance the same concept. Nor does every noun appearing in a Domain Model automatically become a Domain Object. Selection is based on boundaries of Responsibility, Identity, Lifecycle, and Relationships.

When an umbrella term is useful, both are referenced through the same vocabulary; when discussing structure or runtime behavior, Classifiers and Instances are distinguished.

SimpleModeling treats the following as representative Domain Classifiers.