Your company is asking you to build a simplified Customer Relationship Management sys- tem in order to manage all the information about contacts made by salespeople. For each contact the following information is available: their surname, their rst name, the company they are based in, their phone number and their email address. For each company the following information is available: its name, its address, its na- tional identi cation number. Multiple contacts can be based in the same company.

Each salesperson wants their own list of contacts.

Management wants salespeople to share their information. Still, some salespeople do not want to share their contacts. So it has been decided that a salesperson will have to allow another salesperson to see each contact (i.e. Salesperson a has to give Salesperson b permission to view Contact c for each contact they want to share). Only the owner of a contact can grant viewing permission to other salespeople.

Build a physical relational model