Entity- Relationship model (chapter-05)

Headings

• ER concept and terminology.
• Entities, Relationship and attribute.
• ER Diagrams.
• Mapping conceptual model into relational schema.
• Introduction to ERR modelling
• ER concept and terminology.
• Entities, Relationship and attribute.
• ER Diagrams.
• Mapping conceptual model into relational schema.
• Introduction to ERR modelling
• ER concept and terminology.

ER concept and terminology.

• The basic building blocks of all data models are 

1. Entities
2. Attributes
3. Relationships
4. Constraints                 

Entities

• An entity represents a particular type of object the real world.
• An entity is"distinguishable"_ that is ,each entity occurrence is unique and distinct.
• An entity is a person,place,thing,or event about which data will be collected and stored. For example ,                                          
  a CUSTOMER entity would have many distinguishable customer occurrences, such as John Smith, Pedro Dinamita , and Tom Strickland.

• Entities may be physical objects,such as customers or products,but entities may also be abstractions,such as flight routes or musical concerts.

Attribute

• An attribute is a characteristic of an entity .
• 
  

Database Design Process - Chapter 03

Database Design Process 

After studying this chapter, you should be able to:

• Major Topic From Module  

               – Database Design process

•  Lesson title: Database System Development Life cycle.
• After studying this chapter, you should be able to(Learning Outcomes):

– Explain Database system Development

Lifecycle(DSDLC).

– State the stages/Phases of DSDLC.

– Explain each main stages of the DSDLC.

– Explain Database Design process.

Introduction

What are main phases in System Development Life

Cycle (SDLC)?

Database System Development Life Cycle

• Database system is a fundamental component of the larger organization.
• It is also a fundamental and important component of information system.
• Database system development life cycle is inherently associated with the life cycle of the       information system.
• With a small number of users, the life cycle need not be very complex.
• Designing a medium to large database systems with tens to thousands of users, using   hundreds of queries and application programs, the life cycle can become extremely complex.

Stages of DSDLC

• Database planning
• System definition
• Requirements collection and analysis
• Database design
• DBMS selection (optional)
• Application design
• Prototyping (optional)
• Data conversion and loading
• Implementation
• Testing
• Operational maintenance

Stages of DSDLC

üDatabase Planning

• Planning how the stages of 

the life cycle can be realized 

most efficiently and 

effectively.

Stages of DSDLC

üDatabase Planning

üSystem definition

• Specifying the scope and 

boundaries of the database 

system, including the major 

user views, its users, and 

application areas.

Stages of DSDLC

üDatabase Planning

üSystem definition

üRequirements collection and analysis

• Collection and analysis of

the requirements for the

new database system.

Stages of DSDLC

üDatabase Planning

üSystem definition

üRequirements collection and analysis

üDatabase design

• Conceptual, logical, and physical design of the database.

Stages of DSDLC

üDatabase Planning

üSystem definition

üRequirements collection and analysis

üDatabase design

üDBMS selection (optional)

• Selecting a suitable DBMS

for the database system.

Stages of DSDLC

üDatabase Planning

üSystem definition

üRequirements collection and analysis

üDatabase design

üDBMS selection (optional)

üApplication design

• Designing the user interface and the application programs that use and process the database.

Stages of DSDLC

üDatabase Planning

üSystem definition

üRequirements collection and analysis

üDatabase design

üDBMS selection (optional)

üApplication design

üPrototyping (optional)

• Building a working model of the database system, which allows the designers or users to visualize and evaluate how the final system will look and function.

Stages of DSDLC

üDatabase Planning

üSystem definition

üRequirements collection and analysis

üDatabase design

üDBMS selection (optional)

üApplication design

üPrototyping (optional)

üImplementation

• Creating the physical database definitions and the application programs

Stages of DSDLC

üDatabase Planning

üSystem definition

üRequirements collection and analysis

üDatabase design

üDBMS selection (optional)

üApplication design

üPrototyping (optional)

üImplementation

üData conversion and loading

• Loading data from the old system to the new system and, where possible, converting any existing applications to run on the new database.

Stages of DSDLC

üDatabase Planning

üSystem definition

üRequirements collection and analysis

üDatabase design

üDBMS selection (optional)

üApplication design

üPrototyping (optional)

üImplementation

üData conversion and loading

üTesting

• Database system is tested for errors and validated against the requirements specified by the users.

Stages of DSDLC

üDatabase Planning

üSystem definition

üRequirements collection and analysis

üDatabase design

üDBMS selection (optional)

üApplication design

üPrototyping (optional)

üImplementation

üData conversion and loading

üTesting

üOperational maintenance

• Database system is fully implemented.

• The system is continuously monitored and maintained.

• When necessary, new requirements are incorporated into the database system through the preceding stages of the life cycle.

Stages of DSDLC

üDatabase Planning

üSystem definition

üRequirements collection and analysis

üDatabase design

üDBMS selection (optional)

üApplication design

üPrototyping (optional)

üImplementation

üData conversion and loading

üTesting

üOperational maintenance

• Stages of the database system development life cycle are not strictly sequential, Some of them working as feedback loops.

                                         Database system Development Life cycle

Stages of DSDLC

Database Planning

• Database planning must be integrated with the overall Information System strategy of the organization.

• Define the mission statement

– An important first step in database planning..

– The mission statement defines the major aims of the database system.

Ex of Care:- To serve individuals and families in the poorest communities in the world.

– This statement define by Director/owner of the company.

• Identifying the mission objectives

– Next activity involves identifying the mission objectives.

– Define Objective:- A specific result that a person or system aims to achieve within a time frame and with available resources.

– Each objective identify each tasks.

– The assumption is that if the database system supports the mission objectives then the mission statement should be met.

• Database planning also include following

Questions.

– how data will be collected?

– what necessary documentation will be needed?

– how design and implementation should proceed?

System Definition

• Describes the scope and boundaries of the database application and definition the major user views.

• A database have more than one users.

• Identifying user view is an important aspect.

• User view Defines what is required of a database system from the position of a particular job role.

Requirements Collection and Analysis

• The process of collecting and analyzing information(Same as SAD).

• Identify the requirements for the new system.

• Collection methods are

1. Interview

2. Questionnaires

3. Onsite observations

Database Design

• The process of creating a design that will support the enterprise’s mission statement and mission objectives for the required database system.

• There are three phases of database design

– Conceptual

– Logical,

– Physical Design

Conceptual database design

• Conceptual database design, and involves the creation of a conceptual data model of the part of the large project.

• Data model build according to user’s requirement.

• Conceptual database design independent from

– DBMS Software

– Application program

– Programming language

– Hardware

Conceptual database design

• Identify Entities and attributes.

• Draw the E-R diagram.

• The conceptual data model is a source of information for logical database design.

Logical database design

• The process of constructing a model of the data based on a specific data model

• Independent of a particular DBMS and other physical considerations.

• The logical data model is based on the target data model for the database

• The model is tested and validated against the users’

requirements

• Normalization technique used for test the correctness of the data model.

Logical database design

• The logical data model is a source of information for the physical database design.

• The logical model also serves an important role during the operational maintenance stage.

• Logical structure for the database, which describes relations and constraints.

Physical database design

• It is the third and final phase of the database design process,

• Here designer decides how the database is to be implemented.

• Developing the physical database design, we must first identify the target DBMS.

• Therefore, physical design is adjust to a specific

DBMS system.

Physical database design

• physically implement the logical database design.

– creating a set of relational tables

– identifying the specific storage structures and access methods for the data.

– designing security protection for the system

DBMS Selection

• If no DBMS exists, you should select a appropriate

DBMS.

• If you are going to select a DBMS first you cans check the feature against requirements.

Application Design

• The design of the user interface and the application programs that use and process the database.

• Database and application design are parallel activities.

• Designing the application programs that access the database and designing the transactions(Database Access methods).

• These interface present the required information in a

‘user-friendly’ way.

Prototyping

• A prototype is a working model that does not normally have all the required features or provide all the functionality of the final system.

• The main purpose of developing a prototype database system

– allow users to use the prototype

– Features of the system that work well,

– Check inadequate or not.

– Suggest improvements.

– New features to the database system.

Implementation

• On completion of the design stages

• Implement the database and the application programs.

• The database implementation is achieved using the

Data Definition Language (DDL) .

• Any specified user views are also implemented at this stage.

Data Conversion and Loading

• Transferring any existing data into the new database and converting any existing applications to run on the new database.

• This stage is required only when a new database system is replacing an old system.

Testing

• The process of running the database system with the intent of finding errors.

• Testing cannot show the absence of faults; it can show only that software faults are present.

Operational Maintenance

• The process of monitoring and maintaining the database system following installation.

• involves the following activities

– Monitoring the performance of the system. If the performance falls below an acceptable level, tuning or reorganization of the database may be required.

– Maintaining and upgrading the database system (when required). New requirements are incorporated into the database system through the preceding stages of the lifecycle.

Summary

• Database Planning

• System definition

• Requirements collection

• and analysis

• Database design

– Conceptual

– Logical,

– Physical Design

• DBMS selection (optional)

• Application design

• Prototyping (optional)

• Implementation

• Data conversion and loading

• Testing

• Operational maintenance

BY: C.SIVAKARAN

JAFFNA COLLEGE OF T0ECHNOLOGY
SRI LANKA