CSC/ECE 517 Fall 2010/ch6 6h mf

Domain Model

The domain model is an object model that encapsulates the rules, logic, and data associated with the problem domain. The purpose of domain modeling is to separate the concern of problem solving from other concerns like the user interface and persistent storage.

Domain objects represent real world entities, both tangible and intangible, encountered in the problem domain. For example, consider the Spring framework PetClinic sample application. In this application, the domain objects include Person, Vet, Owner, Pet, and Visit. Visit is an example of an intangible entity, in other words an abstract concept, that is part of the problem domain. Contrast these domain objects with graphical user interface (GUI) objects like buttons and text fields which are not relevant to the problem domain (in this case, operating a veterinary clinic).

A number of different terms are used to refer to the domain model and related concepts. These include Domain Object Model (DOM), domain layer, business layer, business logic, business logic layer (BLL), business tier, and logic tier. Many of these terms are used when describing multi-tier architectures. The canonical example is the three-tier architecture composed of the a presentation tier, logic tier, and data tier. The presentation tier is responsible for the user interface. The logic tier is responsible for solving problems in the specific domain of the application. The data tier is responsible for storing and retrieving information, typically to and from a database.