As an example we use a database that models an engineering company. The entities to be modeled are the employees (EMP) and projects (PROJ). For each employee, we would like to keep track of the employee number (ENO), name(ENAME), title in the company (TITLE), salary (SAL), identification number of the project(s) the employee is working on (PNO), responsibility within the project (RESP), and duration of the assignment to the project (DUR) in months. Similarly, for each project we would like to store the project number (PNO), the project name(PNAME), and the project budget (BUDGET).