Example Model Consider the following UML class diagram for a simple model describing employees, departments, projects, and their relationships to each other. We extend the model by the following four constraints which place further restrictions on systems conforming to the model. The number of employees working in a department must be greater or equal to the number of projects controlled by the department.
Employees get a higher salary when they work on more projects.
The budget of a project must not exceed the budget of the controlling department. Employees working on a project must also work in the controlling department. The goal of applying the USE tool is to interactively validate the above model and the constraints. Objects and links can be created which constitute a system state reflecting a snapshot of a running system. In every system state, the constraints are automatically checked for validity.