A model is a hierarchical representation of a software system. Models help you understand the structure of the code within a system, by displaying entities that comprise the system.

A model allows you to visualize and navigate through the structure of your software system. There are two types of models: the System model and user models.

The System model shows the existing physical design of the system.

A user model is a hierarchical representation of a software system. It helps you understand the structure of the code within a system, by displaying entities that comprise the system. A model allows you to visualize and navigate through the structure of your software system.

Models allow you to redesign the software system and immediately see the impact of your changes. You can also view relationships between the entities displayed in the model.

Models may be useful for any number of purposes, such as:

illustrating how the software system is packaged
trying multiple experimental architectures
seeing views of subsystems