Answer to Question 1
It is best to use a supertype/subtype hierarchy when there are attributes that apply to some but not all instances of an entity type. For example, if we have an employee entity type and there is an hourly wage attribute that only applies to hourly employees, it may be best to use a supertype/subtype relationship. Another reason for using supertype/subtype relationships is when you have instances of a subtype that participate in a relationship unique to that subtype. For example, if we have a contractor subtype of employee that has a relationship with staffing agency, then it would be best to use supertype/subtype relationship.
Answer to Question 2
FALSE
DNA analysis of phylogenetic relationships among modern and extinct flightless birds by Cooper and c
Relationships between direction of flow of blood and water or air in different vertebrates.
Different ways to depict phylogenetic relationships
The upper panel shows that scores of four diverse samples of boys on a moral reasoning test show a ...
Intracellular relationships involving the glyoxylate cycle in plant cells
Cross-Cutting Relationships