Chapter Two( Data Model)

Objectives Introduction to Data Models What are the Data Models Why they are important Learn how to design a DBMS

2

Data Model: Model: Importance of data model:

Relatively simple representations, usually graphical, of complex real-world data structures

3

Data Model:

Facilitate interaction among the designer(s), the applications programmer(s), and the end user(s)

Database Models:

Hierarchical Model Network Model Relational Model Entity Relationship (ER) Model

5

Entity-Relationship Model (ER-Model)

Purpose of ER Model is to allow the description of an enterprise to be written without the attention to the efficiency or the physical design.

6

Entity-Relationship Model (ER-Model)

A set of basic objects called Entity, and a set of Relationships among objects (Entities)

7

Entity and Entity Set:

Entity: An object that exists and is distinguishable

from other objects Car ? VW?

Entity Set: A set of entities of the same type Entity set needs not be disjoint

(Faculty vs Student)

8

Entity and Entity Set: (Continued)

An entity is represented by a set of attributesStudent(Name, Id, Gpa)

Each attribute has a set of permitted values called Domain (value set)Id: positive integer

9

Relationship and Relationship Sets:

Relationship is an association among two or more entities

Faculty and Course

Relationship Set: is a set of similar relationships

10

Business Rules:

Brief, precise, and unambiguous descriptions of a policies, procedures, or principles within a specific organization

Apply to any organization that stores and uses data to generate information

Description of operations that help to create and enforce actions within that organization’s environment

11

Sources of Business Rules: Company managers Policy makers Department managers Written documentation

Procedures Standards Operations manuals

Direct interviews with the end users

12

Translating Business Rules into Data Model: Standardize company’s view of data Constitute a communications tool between

users and designers Allow designer to understand the nature,

role, and scope of data Allow designer to understand business

processes Allow designer to develop appropriate

relationship participation rules and constraints

Promote creation of an accurate data model

13

Steps in designing a database using ER Model

1. Identifya. Entity setsb. Relationship sets

2. Identify semantic Info. In the relationship sets

3. Define the value sets of attributes4. Organize data into Entity/Relationships

14

Database Lifecycle

1. Analysis: Study and analyze business

requirements Interview managers and users for

the information requirements Develop a system specification

15

Database Lifecycle

2. Design (Data Models) Entity relational model (ER) Unify modeling language (UML)

Check the design

3. Build the Databases/Document/Test Create tables and views, and programs Produce manuals

16

Database Life Cycle

4. Product delivery Load the software Monitor the performance

17

Practice (Analysis):

Discuss a database system for an organization: