Chapter 2 - Business Data Management

Entity-Relationship Diagram (E-R Diagram)

A graphical representation of an entity-relationship model

Entity-Relationship Model (E-R Model)

A logical representation of the data for an organization or for a business area, using entities for categories of data and relationships for associations between entities.

Relationship Type

A meaningful association between (or among) entity types

Entity

A person, a place, an object, an event, or a concept in the user environment about which the organization wishes to maintain data

True

T/F A multivalued attribute may take on more thank once value for a particular entity instance

True

T/F A time stamp is a time value that is associated with a data value

True

T/F Data names should always relate to business characteristics

True

T/F In an E-R diagram, an associative entity is represented by a rounded rectangle

True

T/F Participation is a relationship may be optional or mandatory

True

T/F Relationships represent action being taken using a verb phrase

False

T/F The degree of a relationship is the number of attributes that are associated with it

False

T/F The intent of a business rule is to break down business structure

False

T/F The purpose of data modeling is to document business rules about processes

False

T/F The relationship among the instances of three entity types is called a unary relationship

Entity Type

A collection of entities that share common properties or characteristics

Attribute

A property or characteristic of an entity or relationship type that is of interest to the organization

Unary Relationship

A relationship between instances of a single entity type

Binary Relationship

A relationship between the instances of two entity types

Cardinality Constraint

A rule that specifies the number of instances of one entity that can (or must) be associated with each instance of another entity.

Ternary Relationship

A simultaneous relationship among the instances of three entity types

Entity Instance

A single occurrence of an entity type

Business Rule

A statement that defines or constrains some aspect of the business. It is intended to assert business structure or to control or include certain the behavior of the business

Time Stamp

A time value that is associated with a data value, often indicating when some event occurred that affected the data value

Relationship Instance

An association between (or among) entity instances where each relationship instance associates exactly one entity instance from each participating entity type

Identifier

An attribute (or combination of attributes) whose value distinguishes instances of an entity type

Simple (or atomic) attribute

An attribute that cannot be broken down into smaller components that are meaningful to the organization

Composite Attribute

An attribute that has meaningful component parts (attributes).

Optional Attribute

An attribute that may not have a value for every entity (or relationship) instance with which it is associated

Multivalued attribute

An attribute that may take on more than one value for a given entity (or relationship) instance

Required Attribute

An attribute that must have a volume for every entity (or relationship) instance with which it is associated

Derived Attribute

An attribute whose values can be calculated from related attribute values

Strong Entity Type

An entity that exists independently of other entity types

Associative Entity

An entity type that associates the instances of one or more entity types and contains attributes that are peculiar to the relationship between those entity instances

Weak Entity Type

An entity type whose existence depends on some other entity type

Composite Identifier

An identifier that consists of a composite attribute

False

T/F A Cardinality constraint tells what kinds of properties are associated with an entity

True

T/F A business rule is a statement that defines or constrains some aspect of the business

True

T/F A good data definition is always accompanied by diagrams, such as the entity-relationship diagram

True

T/F A single occurrence of an entity is called an entity instance

False

T/F A ternary relationship is equivalent to three binary relationships

True

T/F An attribute whose values can be calculated from related attribute values is called a derived attribute.

True

T/F An entity is a person, place, object, event, or concept in the user environment about which the organization wishes to maintain data

True

T/F Data modeling is about documenting rules and policies of an organization that govern data.

False

T/F In an E-R diagram, strong entities are represented by double-walled rectangles

False

T/F Most systems developers believe that dat modeling is the least important part of the systems development process.

True

T/F One reason to use an associative entity is if the associative entity has one or more attributes in addition to the identifier

True

T/F The relationship between a weak entity type and its owner is an identifying relationship.

True

T/F When choosing an identifier, choose one that will not change its value often

True

T/F Τhe E-R model is used to construct a conceptual model

Identifying Owner

The entity type on which the weak entity type depends.

Maximum Cardinality

The maximum number of instances of one entity that may be associated with each instance of another entity.

Minimum Cardinality

The minimum number of instances of one entity that may be associated with each instance of another entity

Degree

The number of entity types that participate in a relationship

Identifying Relationship

The relationship between a weak entity type and its owner