Design Database, 3 degrees of Users.

Administrators - They can see all the information in the database.

Managers - They only can see the information of his dependants.

Dependants - Theirs action must be aprovet by the managers.

Wich the best way to implement this in PostGreSQL? There is some database examples doing this? Some OpenSource Project?

I'am designing a Database for doing this, but I don't have sure I'am doing well.

Please give me some advice.