ER Model and Business Rules Questions and Answers

Q: Which of the following statements concerning business rules is true?

Correct answer: It may include restrictions.A business rule constrains what the organisation permits, so restrictions are exactly what it expresses. The other options are the opposite of good practice - rules should be simple enough to be understood by the people who own them, and stating them so that they can be enforced in code is the point of capturing them at all.

Q: When an entity instance may be a member of multiple subtypes or it does not have to be a member of a subtype, it is which of the following?

Correct answer: Overlap with partial specializationThe stem states both rules. May be a member of multiple subtypes makes the specialisation overlapping rather than disjoint, and does not have to be a member makes it partial rather than total. This is the exact complement of the disjoint-and-total case, and the two rules remain independent of each other.

Q: A subtype entity name should be which of the following?

Correct answer: All of the aboveThe naming conventions for a subtype are those for any entity: a singular noun, because the name denotes one instance; concise, because it will be read many times; and meaningful within the organisation, since a name borrowed from a textbook rather than from the business will not be recognised by the people who must validate the model.

Q: Which of the following is not one of the three ways to classify an action assertion?

Correct answer: EnablerThe three classifications are condition, integrity constraint and authorisation - a rule that must be tested, a rule that must always hold, and a rule about who may do what. Enabler is not among them; it names no distinct kind of constraint on behaviour.

Q: Packaged data models are meant to be exactly right straight out of the box.

Correct answer: FalseA packaged model is a starting point built from experience in an industry, and it saves a great deal of the initial work. It still has to be tailored, because no two organisations define their entities identically. Taking one as correct out of the box means adopting someone else’s definitions of the business.

Q: An action assertion is a statement that expresses some aspect of the static structure of the organization.

Correct answer: FalseA statement about static structure is a term or a fact. An action assertion constrains behaviour - what may happen, under what conditions, and by whom. The statement has attached the definition of the structural kind of rule to the name of the behavioural one.

21.

Specialization is which of the following processes?

A.Defining one or more subtypes of the supertype and forming supertype/subtype relationships.
B.Defining one or more supertypes of the subtype and forming supertype/subtype relationships.
C.Defining one or more subtypes of the supertype and not forming supertype/subtype relationships.
D.Defining one or more supertypes of the subtype and not forming supertype/subtype relationships.

Answer: A

Correct answer: Defining one or more subtypes of the supertype and forming supertype/subtype relationships.

Specialisation works downward from the general to the particular: an existing entity type is examined, distinct subgroupings are identified, and subtypes are created and linked to it. Generalisation is the reverse process, starting from several specific entity types and abstracting a common supertype from them.

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22.

Which of the following statements concerning business rules is true?

A.It should be complex.
B.It may include restrictions.
C.It should not be convertible to computer code.
D.All of the above.

Answer: B

Correct answer: It may include restrictions.

A business rule constrains what the organisation permits, so restrictions are exactly what it expresses. The other options are the opposite of good practice - rules should be simple enough to be understood by the people who own them, and stating them so that they can be enforced in code is the point of capturing them at all.

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23.

A supertype/subtype hierarchy has which of the following features?

A.Subtypes at the lower lever in the hierarchy inherit attributes only from their immediate supertype.
B.Attributes are assigned at the highest logical level.
C.Subtypes at the higher lever in the hierarchy inherit attributes only from their immediate subtype.
D.Attributes are assigned at the lowest logical level.

Answer: B

Correct answer: Attributes are assigned at the highest logical level.

An attribute shared by every subtype belongs at the supertype, where it is held once and inherited by all. Pushing it down to the subtypes duplicates it and invites inconsistency. The rule is a matter of placing each attribute as high as it is true, and no higher.

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24.

A subtype discriminator is which of the following?

A.An attribute of the supertype whose values determine the subtype
B.An attribute of the subtype whose values determine the supertype
C.An attribute of the supertype whose values determine the supertype
D.An attribute of the subtype whose values determine the subtype

Answer: A

Correct answer: An attribute of the supertype whose values determine the subtype

The discriminator sits on the supertype because the question it answers - which kind of thing is this - must be answerable before the subtype is known. Its value directs each instance to its subtype: an employee type code of H, S or C sending the instance to hourly, salaried or consultant.

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25.

When an entity instance may be a member of multiple subtypes or it does not have to be a member of a subtype, it is which of the following?

A.Disjoint with total specialization
B.Disjoint with partial specialization
C.Overlap with total specialization
D.Overlap with partial specialization

Answer: C

Correct answer: Overlap with partial specialization

The stem states both rules. May be a member of multiple subtypes makes the specialisation overlapping rather than disjoint, and does not have to be a member makes it partial rather than total. This is the exact complement of the disjoint-and-total case, and the two rules remain independent of each other.

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26.

A subtype entity name should be which of the following?

A.A singular noun
B.Specific to the organization
C.Concise
D.All of the above

Answer: D

Correct answer: All of the above

The naming conventions for a subtype are those for any entity: a singular noun, because the name denotes one instance; concise, because it will be read many times; and meaningful within the organisation, since a name borrowed from a textbook rather than from the business will not be recognised by the people who must validate the model.

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27.

Use of a supertype/subtype relationship is necessary when which of the following exists?

A.An instance of a subtype participates in a relationship that is unique to that subtype.
B.An instance of a subtype participates in a relationship that is the same as the other subtypes.
C.Attributes apply to all of the instances of an entity type.
D.No attributes apply to any of the instances of an entity type.

Answer: A

Correct answer: An instance of a subtype participates in a relationship that is unique to that subtype.

A supertype and subtype structure is justified either by attributes that apply only to some instances or by relationships that only some instances participate in. If every instance behaves alike in both respects there is nothing to separate and the subtypes add complexity without meaning.

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28.

Which of the following is not one of the three ways to classify an action assertion?

A.Condition
B.Integrity Control
C.Authorization
D.Enabler

Answer: D

Correct answer: Enabler

The three classifications are condition, integrity constraint and authorisation - a rule that must be tested, a rule that must always hold, and a rule about who may do what. Enabler is not among them; it names no distinct kind of constraint on behaviour.

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29.

Packaged data models are meant to be exactly right straight out of the box.

A.True
B.False

Answer: B

Correct answer: False

A packaged model is a starting point built from experience in an industry, and it saves a great deal of the initial work. It still has to be tailored, because no two organisations define their entities identically. Taking one as correct out of the box means adopting someone else’s definitions of the business.

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30.

An action assertion is a statement that expresses some aspect of the static structure of the organization.

A.True
B.False

Answer: B

Correct answer: False

A statement about static structure is a term or a fact. An action assertion constrains behaviour - what may happen, under what conditions, and by whom. The statement has attached the definition of the structural kind of rule to the name of the behavioural one.

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