Data Models

Chapter 2

What ia the primary purpose of data modelling in database design?

It acts as a bridge between real worl objects and the computer database structure

In the context of data models, what is the definition of an ‘entity’?

A person, place, thing, concept or event about which data is collected and stored.

Define Attribute

A characteristic of an entity, equivalent to a field in a file system

What term describes an association among multiple entities?

Relationship

Data models use the shorthand notation 1: M to represent which type of relationship?

one-to-many

Which relationship type exists when one occurence of an entity is associated with many occurrences of another, and vice versa?

Many-to-many (M : N)

In a 1:1 relationship, how many instances of a related entity is one entity instance associated with?

Only one

What is a ‘constraint’ in the context of data modeling

A restriction placed on data to ensure its integrity

What is the first step in identifying entities, attributes and relationships for a data model?

identifying the business rules for the problem domain

What is a Business Rule

A brief, precise description of a policy, procedure or principle within an organisation

To ensure they are effective, business rules must be easy to understand and widely ______.

Disseminated

When translating business rules into model components, what do nouns usually become?

Entities

When translating business rules into model components, what do verbs that associate nouns usually become?

Relationships

What is it important to verify business rules with multiple end users?

Users may have different, sometimes inaccurate, perceptions of how a job or process works.

According to naming conventions, how should entity names generally be formatted?

As singular nouns that are familiar to the business (e.g PAINTER instead of PAINTERS)