Database Design

Topics: Database, Database model, Database management system Pages: 10 (739 words) Published: October 30, 2013
Database Design Process
Database Life Cycle

Key points
Database design must reflect the information
system of which the database is a part
Information systems undergo evaluation and
revision within a framework known as the Systems
Development Life Cycle (SDLC)
Databases also undergo evaluation and revision within a
framework known as the Database Life Cycle (DBLC)
There are two general design strategies exist:
top-down vs. bottom-up design
centralized vs. decentralized design

2

The Information System
Database
Carefully designed and constructed repository of
facts
Part of an information system

Information System
Provides data collection, storage, and retrieval
Facilitates data transformation
Includes people, procedures, hardware, and
software

3

The Information System (Con’t.)
System Analysis
Establishes need and extent of an information system
Refer to Recommended Requirements Gathering Practices

We are NOT DOING A SYSTEM REQ’T ANALYSIS!!

Systems development
Process of creating information system

Database development
Process of database design and implementation
Creation of database models

Implementation
Creating storage structure
Loading data into database
Providing for data management
4

Systems Development Life Cycle
System Analysis

Database Lifecycle (DBLC)

5

Database Life Cycle (DBLC)
Phase 1
Phase 2
Phase 3
Phase 4

Phase 5

Phase 6
6

Database
Organization

Phase 1: Database Initial Study
Phase 1

Purposes

Phase 2

Analyze company situation

Phase 3

Operating environment
Organizational structure

Phase 4
Phase 5

Define problems and constraints
Define objectives
Define scope and boundaries

Phase 6

7

Initial Study Activities

8

Phase 2: Database Design
Most Critical DBLC phase
Makes sure final product
meets requirements
Focus on data requirements
Subphases
I. Create conceptual design
II. DBMS software selection
III. Create logical design
IV. Create physical design

9

Phase 1
Phase 2
Phase 3
Phase 4
Phase 5
Phase 6

Two Views of Data

10

I. Conceptual Design
Data modeling creates abstract data structure to
represent real-world items
High level of abstraction
Four steps
Data analysis and requirements
*Entity relationship modeling and normalization*
*Data model verification*

11

Data analysis and Requirements
Focus on:
Information needs
Information users
Information sources

Data sources
Developing and gathering end-user data views
Direct observation of current system
Interfacing with systems design group

Business rules
12

Entity Relationship
Modeling and Normalization

13

E-R Modeling is Iterative

14

Concept Design: Tools and Sources

15

Data Model Verification
E-R model is verified against proposed
system processes
End user views and required transactions
Access paths, security, concurrency control
Business-imposed data requirements and
constraints

Reveals additional entity and attribute details

16

E-R Model Verification Process

17

Iterative Process of Verification

18

II. DBMS Software Selection
DBMS software selection is critical
Advantages and disadvantages need study
Factors affecting purchasing decision
Cost
DBMS features and tools
Underlying model
Portability
DBMS hardware requirements

19

III. Logical Design
Translates conceptual design into internal
model
Maps objects in model to specific DBMS
constructs
Design components
Tables
Indexes
Views
Transactions
Access authorities
Others
20

IV. Physical Design
Selection of data storage and access
characteristics
Very technical
More important in older hierarchical and network
models

Becomes more complex for distributed systems
Designers favor software that hides physical
details

21

Phase 3: Implementation and Loading
Creation of special storage-related constructs
to house end-user tables
Data loaded into...
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