Database 2 External Schema

February 23 , 2002 A K Ramani 1

RECAP

Role of Databases

Classification

Evolution of Databases


Aim– General steps in Design &

Development of Databases in context to information system Development process.

Objectives1. Understand Information System

Architecture2. Database Analysis, Design and

Implementation issues3. Design Example

DATABASE DEVELOPMENT PROCESS


Database development Starts with Enterprise Data Modeling (EDM)Steps in EDM

1. Review current system2. Analyse the business area to be supported3. Data requirement4. Plan DB Project (s)

EDM considers general contents of organizational databases. Overall pictureHowever, comprehensive architectural plan of IS development is essentialFeatures

• ISA can grow & expand (vision)• Impact of Technology• Flexible• Eye on standards

ENTERPRISE DATA MODELING


Planning

Budget

Overall direction of IT & decision

Priority areas

BENEFITS OF ISA


Data

Process (DFD, Models)

Network

People

Events & points in time (RTDB)

Reason for Events , Rules

KEY COMPONENTS OF ISA



A Data oriented methodology for development of information systems.

For engineering IS, approach the Top-down methodology is followed where integration of individual system components takes place

IS DEVELOPMENT


Planning : ISA, including EDM (results is an ISA)

Analysis : Conceptual Data Model & Logical data base

Design : Logical / Physical DB Implementation : DB definitions ,

Tables, Indexes , Codes

STEPS OF IS DEVELOPMENT


Goal : To support Business Strategies with IT 3 Steps

1. Identify strategic planning factors – to develop planning context and to link information systems plan to the strategic plan of the organization

• Goals : Growth Rate, Return on Investment ( ROI )……..

• Success Factors : Quality, On-time, Employee productivity…..

• Problem Areas : Competition, Maintenance of records….

IS PLANNING


2. Identify Corporate Planning objects – define the business scope

1. Organizational Units – Various departments

2. Locations – business places

3. Business Functions – business processes like product development

4. Entity Types : Categories of data about people, places & things managed by company

5. Information System : Application S/W & supporting procedures.

IS PLANNING


IS PLANNING

3. Develop Enterprise Model – consists of a functional breakdown , an enterprise data model and various planning matrices.

1. Functional Decomposition – breaking down description of system into finer and finer details, identify important components.

2. High level ER diagram3. Planning Matrices – A format for showing

interrelationships between data entities.– Functions Support Functions– Production Operation Scheduling, Fabrication,

Assembly– Material Management Material requirement planning – - Purchasing– - Receiving– Marketing - Market research– - Order

fulfillment– - Distribution


Develop Enterprise Model– Decompose business function

– Planning Matrixes (using ER)

Functional decomposition helps in simplify problems , identify important components.

Functions Support Functions

Production Operation Scheduling, Fabrication, Assembly

Material Management Material requirement planning

- Purchasing

- Receiving

Marketing - Market research

- Order fulfillment

- Distribution


Sample Planning Matrix – for Order Fulfillment– Identify 1 or more database (s) ,keeping in mind

Enterprise view

– Develop ER models,describe each entity,business rules

– Develop planning Matrixes,linking various components

X

Business Function

Business Planning

Material Manage

Finance & Accts

Cus

tom

er

Pro

duct

Invo

ice

Em

ploy

ee

Data/Entity

X X X

X X

X X X

PLANNING MATRIX


Advantages

– Identify Orphans : indicate which data entities are not used by any function or which functions do not use any entities

– Spot Missing Entities – Prioritize Development

PLANNING MATRIX


Types of Planning Matrices – Location to Function : which business functions

are performed at which business locations– Unit to Function : which business functions are

performed at which business units– Information System to Data Entity : explains

how each information system interacts with data entity

– Supporting Function to Data Entity : Identified which data are captured , used , updated or deleted within each function

– Information System to Objective : Shows which information system support which business objective

PLANNING MATRIX


Project Identification & selection

Project Initiation & Planning

Analysis

Logical Design

Physical Design

Implementation

Maintenance

Enterprise Model

Conceptual Data Model

DATABASE DEVELOPMENT PROCESS

Logical Data Base Design

Physical Design

Database Implementation

Database Maintenance

Database Development SDLC


In SDLC total specifications of IS is developed in piecesSteps may overlapEnterprise model– Data needed for each IS, general contents of Data

base Conceptual Data Modeling– Entities & Relationships– Detailed Data model (Data base Analyst)– Identifying all organizational data– Business relationship– Rules for data integrity– Model may require improvements – ER,EER…..

SDLC and DBMS APPROACH


Logical Database Design– Transform conceptual model Relations that are

specific to DBMS used– Transactions, reports,displays to be supported– What data are to be maintained in DB?– Several users views to be integrated – Normalization : Process of designing well

structured relations, avoid unnecessary duplication of data.

Physical DB Design– Identify programs to process transactions,

generate reports– Efficiency , Security– H/W, OS, Network

SDLC and DBMS APPROACH


Database Implementation– Create DB definition, Code, test,

populate

– SQL,VB, C

– Train, Document, backup

RAD

ProblemEarly Prototype

ImplementationProblem

Conceptual Data Model

Prototyping Logical Data Base

Code & Contents

Analyse, Improve

Revise

DBMS APPROACH


– Automated support to assist system Development process

– Draw data models using entity relationship

– Generate code• Database definition commands

DBMS• Compose SQL commands

– An information repository, which contains information needed to generate diagram, forms, reports.

CASE TOOLS


System Analyst Analyze BusinessData base Analyst Data base

ComponentUser NeedsProgrammer CodingDatabase Administrator Computer Architecture experts

Construct GANTT/PERT ChartsReview Points

Senior DB/System Analyst is LEADER

PROJECT DEVELOPMENT


Users ViewConceptual SchemaPhysical or Internal Schema

ANSI Architecture

User-1 User-2 User-n- - -

Conceptual Scheme

Internal Scheme

Physical DB

External Level

Conceptual Level

Internal Level

MODEL / VIEW OF DATABASES


Data Independence is achieved by Inter-level MappingQueries are translated between levels automaticallyConceptual schema is encapsulated (independent of Database Management Technology)Physical schema is also encapsulated (specs to allocate & manage secondary memory)

Develop Conceptual Schema

Develop User View

Physical Schema

CA Features Performance

Enterprise

Data Model

User

Needs

MODEL / VIEW OF DATABASES


Centralized DB System

Database

DBMS

DATABASES ARCHITECTURES


Data Manager

Transaction Manager D

B

Distributed DB System



Client Server DB

Client : User System Interface & localized Data

Sever : Shared Data

CLIENT

CLIENT

SERVER

DB

DBMS



Client Server (2 Tired)

• Thin Client / Fat Server• Fat Client / Thin Server

DB Server

Server



Client Server (3 Tiered)

DB Server

Client (s)DATABASE

Dept. Server

(Application Server)

Organizational Server (Higher Level)

Merging or Data



DB –Driven Web Applications

AdvantagesMulti –processingAdvantages of each computer platform (PCs, Servers)Mix Client Technologies (Thin Client)Processing close to data , reduces trafficOpen System Standards

DB Server

WEB+Application Server

Internet



Summary

General steps in DB development

ISA, EDM

DB Architectures

Education

Database 2 External Schema