Section 4

Question 1

You can typically associate ‘………………’ of something with supertypes and subtypes

Answer 1

choices

• food order types (eat in, to go)
• grocery bag types (paper, plastic)
• payment types (check, cash, credit)

Question 2

Often some instances of an entity have attributes and/or relationships that other instances do not have

Answer 2

• Imagine a business which needs to track payments from customers
• Customers can pay by cash, by check, or by credit card

Question 3

Sometimes it makes sense to subdivide an entity into ………….. In this case, the entity is called a “……………” and each group is called a “………….”

Answer 3

subtypes / supertype / subtype

Question 4

(creating supertype and subtype is may be the case when a group of instances has special properties, such as ………… or ……………….. that exist only for that group

Answer 4

attributes / relationships

• Should we create a single PAYMENT entity or three separate entities CASH, CHECK, and CREDIT CARD?*
• And what happens if in the future we introduce a fourth method of payment?*

Question 5

A subtype

1. Inherits all ……….. of the supertype
2. Inherits all ………… of the supertype
3. Is ………. ………. the supertype
4. Never ………. ………
5. Usually has its own …………. or ………..
6. May have ……….. of its own

Answer 5

1. attributes
2. relationships
3. drawn within
4. exists alone
5. attributes / relationships
6. subtypes

Question 6

When an ER model is complete, subtypes never stand alone. In other words, if an entity has a subtype, a second subtype must also exist, this makes sense. A single subtype is exactly the same as the supertype

Answer 6

R 2

Question 7

This idea leads to the two subtype rules:

1. …………: Every instance of the supertype is also an instance of one of the subtypes. All subtypes are listed without omission
2. ……….. ………….: Each instance of a supertype is an instance of only one possible subtype

Answer 7

1. Exhaustive
2. Mutually Exclusive

Question 8

At the conceptual modeling stage, it is good practice to include an ………. subtype to make sure that your subtypes are exhaustive – that you are handling every instance of the supertype

Answer 8

OTHER

Question 9

When a need exists within the business to show …………. and …………. between instances, then subtype

Answer 9

similarities / differences

being able to subtype is not the issue—having a reason to subtype is the issue

Question 10

When modeling supertypes and subtypes, you can use three questions to see if the subtype is correctly identified:

1. Is this subtype a ………… of supertype?
2. Have I covered all possible cases? (…………..)
3. Does each instance fit into one and only one subtype? (………… ………..)

Answer 10

1. kind
2. exhaustive
3. mutually exclusive

Question 11

You can nest subtypes. For ease of reading – “readability” – you would usually show subtypes wit only ………. levels, but there is no rule that would stop you from going beyond two levels

Answer 11

two

Question 12

………… …………. rules indicate the types of information to be stored (attributes) and how the information elements interrelate (relationships)

Answer 12

Structural business

Structural business rules can nearly always be diagrammed in the ERD

Question 13

Procedural rules deal with the prerequisites, ……….., ……….., or …………. requirements of a business

Answer 13

steps / processes / workflow

Many procedural business rules are related to time: event A must happen before event B