"Given the following business scenario, create a Crow's Foot ERD using a specialization hierarchy if appropriate.
Two-Bit Drilling Company keeps information on employees and their insurance dependents. Each employee has an employee number, name, date of hire, and title. If an employee is an inspector, then the date of certification and the renewal date for that certification should also be recorded in the system. For all employees, the Social Security number and dependent names should be kept. All dependents must be associated with one and only one employee. Some employees will not have dependents, while others will have many dependents.
In this scenario, a specialization hierarchy is appropriate because there is an identi?able type or kind of employee (Inspectors), and additional attributes are recorded that are speci?c to just that kind or type. It is worth noting that if there is only a single subtype, the disjoint/overlapping designation may be omitted - if there is only one subtype then there is no other subtype to overlap or be disjoint from. Also, when there is only a single subtype, the completeness constraint is always partial completeness. If the completeness constraint were identi?ed as total completeness, that would mean that every employee must be an inspector, in which inspector would be a synonym for employee not a kind of employee.