Modeling Data in the Organization Questions and Answers

Answer: B

Correct answer: False

Business rules are specific to the organisation that adopts them, which is exactly why they must be captured rather than assumed. Two firms in the same trade will define a customer, a sale or an active account differently, and a model built on the modeller’s assumptions rather than the organisation’s rules will be wrong in ways nobody notices until late.

Answer: A

Correct answer: True

A time stamp records when a value applied, which is what makes a time-varying attribute possible: an employee’s salary is not one value but a series of values each with the period it held for. Storing history this way is how a database answers questions about the past rather than only the present.

Answer: A

Correct answer: True

The entity-relationship model is a logical representation of an organisation’s data - what exists and how it relates - independent of how it will be stored or of what software will hold it. That independence is what lets the same model be implemented on different products, and what makes it worth validating with users.

Answer: B

Correct answer: False

A word or phrase with a specific meaning for the business is a term. A fact is an association between two or more terms, such as a customer placing an order. Terms and facts together are the raw material from which entities, attributes and relationships are drawn.

Answer: D

Correct answer: All of the above.

The conventions all serve readability. A singular noun, because the name denotes one instance rather than a collection; concise, because it appears repeatedly on diagrams and in code; and specific to the organisation, because a name taken from a textbook rather than from the business will not be recognised by the people who must validate the model.

Answer: B

Correct answer: False

An entity-relationship diagram models data, not the ways it will be presented. Reports are outputs produced from the data by applications, and including them would confuse the conceptual model with the systems built on it - and would tie the model to today’s reporting requirements.

Answer: B

Correct answer: 3

Ternary means exactly three entity types participating in a single relationship, and it is genuinely different from three binary relationships between the same entities - a fact linking a supplier, a part and a project is not recoverable from three pairwise associations. It is usually implemented as an associative entity.

Answer: A

Correct answer: True

This is the definition. Cardinality is read in both directions and expressed as a minimum and a maximum at each end, and those four figures together determine both whether participation is required and how many instances are permitted.

Answer: B

Correct answer: False

Multiple and binary are unrelated terms. Binary describes the degree of a relationship, meaning two entity types take part. Multiple describes an attribute that can hold more than one value for a single instance. Confusing the two mixes up a property of relationships with a property of attributes.

Answer: D

Correct answer: Cannot tell

A minimum of one establishes that participation is mandatory but says nothing about how many are permitted. Mandatory one and mandatory many both have a minimum of one, and only the maximum distinguishes them - which is why both figures must always be read together.