Data Modeling Basics

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Questions and Answers

What is the basic logical structure of the hierarchical model represented by?

A grid

A linear sequence

An upside-down tree (correct)

A circular diagram

In the hierarchical model, how many parents can a child have?

None

Two

One (correct)

Many

What characteristic distinguishes the network model from the hierarchical model?

Children can only belong to one parent

It does not impose any database standards

Data is organized in a linear fashion

Records can have multiple parents (correct)

What is one of the main purposes of the network model?

To improve database performance Signup and view all the answers

Which of the following models allows for a parent to have multiple children?

Hierarchical Model Signup and view all the answers

What is the primary purpose of a data model?

To provide a graphical representation of data for communication Signup and view all the answers

Which of the following describes an attribute in a data model?

A characteristic of an entity Signup and view all the answers

Which relationship type allows for one instance of an entity to relate to multiple instances of another entity?

One-to-Many (1:M) Signup and view all the answers

What must business rules be in order to effectively communicate within an organization?

Simplicity-focused and easily understood Signup and view all the answers

Which of the following is NOT a source of business rules?

Customer feedback Signup and view all the answers

How can nouns in business rules be translated when developing a data model?

Into entities Signup and view all the answers

What characteristic must a data model have to accommodate different user needs?

It serves as an abstraction of real-world objects Signup and view all the answers

What role do verbal descriptions play in business rules?

They translate into relationships between entities Signup and view all the answers

Which of the following correctly describes a constraint in the context of data models?

A limitation on what data can be entered or stored Signup and view all the answers

What is the significance of understanding relationship participation rules in a data model?

They enable the designer to develop accurate associations among entities Signup and view all the answers

What is a characteristic of a relational table?

It consists of row/column intersections. Signup and view all the answers

Which component does the SQL 'engine' perform?

It executes all queries. Signup and view all the answers

What does the Entity Relationship Diagram (ERD) primarily represent?

Entities and their relationships. Signup and view all the answers

What notation is used in the Entity Relationship Model to represent relationships?

Chen notation Signup and view all the answers

Which statement about the physical model is true?

It specifies how data is saved on storage media. Signup and view all the answers

How are relationships represented in Crow’s Foot notation?

By diamonds Signup and view all the answers

Why were relational models considered impractical in 1970?

They required a lot of computer overhead. Signup and view all the answers

What does physical independence in the relational model imply?

Changes to the physical model do not affect the internal model. Signup and view all the answers

Which of the following best describes the role of an end-user interface in an SQL-based relational database?

It allows users to interact with the data. Signup and view all the answers

In relational database design, how are rows in different tables typically related?

Through common values in common attributes. Signup and view all the answers

Study Notes

Data Modeling and Data Models

Relatively simple representations of complex real-world data structures.
Often graphical.
A model is an abstraction of a real-world object or event.
Useful in understanding complexities of the real-world environment.
Data modeling is iterative and progressive.

The Importance of Data Models

Facilitate interaction among the designer, the applications programmer, and the end-user.
End-users have different views and needs for data.
Data models organize data for various users.
A data model is an abstraction.
Cannot draw required data out of the data model.

Data Model Basic Building Blocks

Entity: Anything about which data is collected and stored.
Attribute: A characteristic of an entity.
Relationship: Describes an association among entities.
- One-to-Many (1:M) relationship
- Many-to-Many (M:N or M:M) relationship
- One-to-One (1:1) relationship
Constraint: A restriction placed on the data.

Business Rules

Descriptions of policies, procedures, or principles within a specific organization.
Apply to any organization that stores and uses data to generate information.
Description of operations to create/enforce actions within an organization’s environment.
Must be in writing and kept up-to-date.
Must be easy to understand and widely disseminated.
Describe characteristics of data as viewed by the company.

Discovering Business Rules

Sources of business rules:
- Company managers
- Policy makers
- Department managers
- Written documentation
  - Procedures
  - Standards
  - Operations manuals
- Direct interviews with end-users

Translating Business Rules into Data Model Components

Nouns translate into entities.
Verbs translate into relationships among entities.
Relationships are bidirectional.
Two questions to identify the relationship type:
- How many instances of B are related to one instance of A?
- How many instance of A are related to one instance of B?

Hierarchical Model

Developed in the 1960s to manage large amounts of data for manufacturing projects.
Basic logical structure is represented by an upside-down “tree”.
Structure contains levels or segments.
Each parent can have many children, but each child has only one parent (also known as a one-to-many relationship).

Network Model

Created to represent complex data relationships more effectively than the hierarchical model.
Improves database performance.
Imposes a database standard.
Resembles hierarchical model.
Record may have more than one parent.

The Relational Model

Developed by E.F.Codd (IBM) in 1970.
Table (relations):
- Matrix consisting of row/column intersections.
- Relational table stores a collection of related entities.
SQL-based relational database application involves three parts:
- End-user interface:
  - Allows the end-user to interact with the data.
- Set of tables stored in the database:
  - Each table is independent from another.
  - Rows in different tables are related based on common values in common attributes.
- SQL "engine":
  - Executes all queries.

The Entity Relationship Model

Widely accepted standard for data modeling.
Introduced by Chen in 1976.
Graphical representation of entities and their relationships in a database structure.
Entity Relationship Diagram (ERD):
- Uses graphic representations to model database components.
- Entity is mapped to a relational table.
Entity instance (or occurrence) is a row in a table.
Entity set is a collection of like entities.

The Physical Model

Operates at the lowest level of abstraction.
Describes the way data is saved on storage media such as disks or tapes.
Requires the definition of physical storage and data access methods.
Relational model aimed at the logical level.
Does not require physical-level details.
Physical independence: changes in the physical model do not affect the internal model.

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Description

This quiz covers fundamental concepts of data modeling, including the significance of data models, basic building blocks such as entities, attributes, relationships, and constraints. Additionally, it explores the interactions among users, designers, and programmers and the importance of business rules in data modeling.