Exam 5: Data Modeling With the Entity-Relationship Model

An attribute that determines which subtype is appropriate is called a discriminator.

Data modelers agree that weak,non-ID-dependent entities exist and are important.

An exclusive subtype pattern has one supertype entity that relates to one or more subtype entities.

Common variants of the E-R model include:

The degree of a relationship is expressed as the relationship's maximum cardinality.

Relationships of degree two are referred to as binary relationships.

All weak entities must have a minimum cardinality of 1 on the entity on which it depends.

Entities of a given type are grouped into entity classes.

An entity instance of an entity class is the representation of a particular entity and is described by the values of the attributes of the entity.

A data model is a plan for a database design.

Which of the following is considered to be a weak entity?

In E-R modeling,an attribute describes the characteristics of an entity.

You are given an E-R diagram with two entities,ORDER and CUSTOMER,as shown above,and are asked to draw the relationship between them.If a given customer can place only one order and a given order can be placed by at most one customer,which of the following should be indicated in the relationship symbol between the two entities?

The method of constructing data models used in the text is the extended entity-relationship (E-R)model.

Relationships between supertypes and subtypes are called IS-A relationships.

An identifier may be ________.

What is meant by the cardinality of a relationship?

The characteristics of a thing are described by its ________.

A relationship's maximum cardinality indicates the maximum number of entities that can participate in the relationship.

One example of a database design using a strong relationship is the multivalued attribute pattern.