Chapter 7

Identifier

A candidate key that has been selected as the unique identifying characteristic for an entity type.

Entity Type

A collection of entities that share common properties or characteristics.

Conceptual Data Model

A detailed model that shows the overall structure of organizational data while being independent of any database management system or other implementation considerations.

Entity-Relationship (E-R) Diagram

A graphical representation of the entities, associations, and data for an organization or business area; it is a model of entities, the associations among those entities, and the attributes of both the entities and their associations.

Attribute

A named property or characteristic of an entity that is of interest to the organization.

Design Strategy

A particular approach to developing an information system. It includes statements on the system's functionality, hardware and system software platform and method for acquisition.

Entity

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

Binary Relationship

A relationship between instances of two entity types.

Unary (Recursive) Relationship

A relationship between the instances of one entity type.

Repeating Group

A set of two or more multivalued attributes that are logically related.

Ternary Relationship

A simultaneous relationship among instances of three entity types.

Entity Instance

A single occurrence of an entity type.

Relationship

An association between the instances of one or more entity types that is of interest to the organization.

Candidate Key

An attribute (or combination of attributes) that uniquely identifies each instance of an entity type.

Multivalued Attribute

An attribute that may take on more than one value for each entity instance.

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.

Degree

The number of entity types that participate in a relationship.

Cardinality

The number of instances of entity B that can (or must) be associated with each instance of entity A.