Modeling Data in the Organization Questions and Answers

Q: A good business rule is which of the following?

Correct answer: DeclarativeA good business rule states what must be true rather than how to achieve it, so it can be implemented in whatever way suits the technology and can be validated by the people who own it. The other three are faults: imprecision leaves it unenforceable, redundancy invites contradiction, and a compound rule should be split into its parts.

Q: A derived attribute is an attribute whose values can be calculated from a related relationship.

Correct answer: FalseA derived attribute is calculated from other attribute values - an age from a date of birth, a total from unit price and quantity. Deriving it from a relationship is not the definition. The reason for marking it as derived is that its value must never be stored and updated independently of the values it comes from.

Q: A binary relationship is which of the following?

Correct answer: A relationship between two entitiesThe degree of a relationship counts the entity types taking part: unary for one, binary for two, ternary for three. Binary relationships are by far the commonest, and a relationship of higher degree can often be replaced by an associative entity joined to each participant by a binary relationship.

Q: If there are two entities with a relationship between them, and one of the entities is completely dependent on the other, then which of the following must exist?

Correct answer: Weak entityAn entity that cannot exist without another - a dependant without an employee, a line item without an order - is a weak entity, and the relationship joining it to the entity it depends on is an identifying relationship. Its identifier includes the identifier of the owner, since it has no independent existence to be identified by.

Q: When the minimum and maximum number of instances of an entity is one, you know which of the following?

Correct answer: Mandatory oneThe two figures answer two different questions. The minimum says whether participation is required: one means it is, so the relationship is mandatory. The maximum says how many are permitted: one means at most a single instance. Together they give mandatory one.

Q: An attribute name should be which of the following?

Correct answer: Follow a standard formatAttribute names should follow a consistent convention across the model, typically including the entity name or an abbreviation of it, so that the same concept is named the same way everywhere. They are nouns rather than verbs, and aliases are recorded in the repository rather than used as names.

Q: An attribute is a person, place, object, event in a user environment.

Correct answer: FalseA person, place, object or event in the user environment is an entity. An attribute is a property or characteristic of an entity - the employee’s name, the order’s date. The statement has given the definition of one under the name of the other.

Q: No two attributes of the same entity type should have the same name.

Correct answer: TrueTwo attributes of the same entity type with the same name could not be told apart, so uniqueness within the entity is a requirement rather than a convention. Across entity types the same name may recur - both a customer and a supplier have a name - which is why the naming standard usually qualifies attributes with their entity.

Q: A relationship is an association representing the interaction between attributes.

Correct answer: FalseA relationship associates entities, not attributes. Attributes describe the entities and relationships they belong to; they do not associate with one another. Substituting one term for the other reverses the structure of the model entirely.

Specialization Lattice stands for

A.An entity type can participate as a subclass in only one specialization.
B.An entity type can participate as a subclass in more than one specialization.
C.An entity type that can participate in one specialization.
D.An entity type that can participate in one generalization.

Exam Year(s)

UGC NET - 2014,

Answer: B

A specialization lattice lets an entity type be a subclass in more than one specialization.

In the extended ER model a hierarchy gives each subclass one superclass, but a lattice allows a subclass to take part in several specializations.

Options A, C and D describe participation in only one specialization or in a generalization, which restricts it. In the extended entity-relationship model a specialization hierarchy gives each subclass one superclass, whereas a lattice allows an entity type to be a subclass of several superclasses and so to take part in more than one specialization.

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A good business rule is which of the following?

A.Declarative
B.Imprecise
C.Redundant
D.Compound

Answer: A

Correct answer: Declarative

A good business rule states what must be true rather than how to achieve it, so it can be implemented in whatever way suits the technology and can be validated by the people who own it. The other three are faults: imprecision leaves it unenforceable, redundancy invites contradiction, and a compound rule should be split into its parts.

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A derived attribute is an attribute whose values can be calculated from a related relationship.

A.True
B.False

Answer: B

Correct answer: False

A derived attribute is calculated from other attribute values - an age from a date of birth, a total from unit price and quantity. Deriving it from a relationship is not the definition. The reason for marking it as derived is that its value must never be stored and updated independently of the values it comes from.

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A binary relationship is which of the following?

A.A relationship between two attributes
B.A relationship between two entities
C.An attribute with two different relationships
D.An entity with two different relationships

Answer: B

Correct answer: A relationship between two entities

The degree of a relationship counts the entity types taking part: unary for one, binary for two, ternary for three. Binary relationships are by far the commonest, and a relationship of higher degree can often be replaced by an associative entity joined to each participant by a binary relationship.

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If there are two entities with a relationship between them, and one of the entities is completely dependent on the other, then which of the following must exist?

A.Derived attribute
B.Optional one cardinality
C.Multi-valued attribute
D.Weak entity

Answer: D

Correct answer: Weak entity

An entity that cannot exist without another - a dependant without an employee, a line item without an order - is a weak entity, and the relationship joining it to the entity it depends on is an identifying relationship. Its identifier includes the identifier of the owner, since it has no independent existence to be identified by.

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When the minimum and maximum number of instances of an entity is one, you know which of the following?

A.Mandatory one
B.Optional one
C.Mandatory many
D.Cannot tell

Answer: A

Correct answer: Mandatory one

The two figures answer two different questions. The minimum says whether participation is required: one means it is, so the relationship is mandatory. The maximum says how many are permitted: one means at most a single instance. Together they give mandatory one.

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An attribute name should be which of the following?

A.Singular verb or verb phrase
B.Follow a standard format
C.Use a alias
D.All of the above.

Answer: B

Correct answer: Follow a standard format

Attribute names should follow a consistent convention across the model, typically including the entity name or an abbreviation of it, so that the same concept is named the same way everywhere. They are nouns rather than verbs, and aliases are recorded in the repository rather than used as names.

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An attribute is a person, place, object, event in a user environment.

A.True
B.False

Answer: B

Correct answer: False

A person, place, object or event in the user environment is an entity. An attribute is a property or characteristic of an entity - the employee’s name, the order’s date. The statement has given the definition of one under the name of the other.

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No two attributes of the same entity type should have the same name.

A.True
B.False

Answer: A

Correct answer: True

Two attributes of the same entity type with the same name could not be told apart, so uniqueness within the entity is a requirement rather than a convention. Across entity types the same name may recur - both a customer and a supplier have a name - which is why the naming standard usually qualifies attributes with their entity.

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10.

A relationship is an association representing the interaction between attributes.

A.True
B.False

Answer: B

Correct answer: False

A relationship associates entities, not attributes. Attributes describe the entities and relationships they belong to; they do not associate with one another. Substituting one term for the other reverses the structure of the model entirely.

Discuss in Forum

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