Database Systems: Design, Implementation, and Management Chapter 9 Database Design.

Database Systems: Design, Implementation, and Management

Chapter 9Database Design

The Systems Development Life Cycle (SDLC)

• Traces history (life cycle) of information system

• Database design and application development mapped out and evaluated

• Iterative rather than sequential process

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JMSB BTM and the SDLC

BTM Minor

Entire SDLC

Technology Acceptance Model

http://www.istheory.yorku.ca/Technologyacceptancemodel.htm

Davis, F. D. (1989). Perceived usefulness, perceived ease of use, and user acceptance of information technology. MIS Quarterly, 13(3), 319-339.

Two fundamental issues in deciding how much functionality to implement in a new system• How much functionality should you implement?

(Perceived Usefulness)1. Baseline replication: The new system must at least be as

functional as the old one2. User-requested functionality: The system should add new

features required by users3. Analyst-suggested functionality: The system may optionally

go beyond users’ expectations• How much retraining effort would it take users to learn to

use the new system? (Perceived Ease of Use)1. Baseline replication: Minimal effort, or net zero effort (takes

no more effort than time and effort saved from switching from old system)

2. User-requested functionality: Users must feel that new retraining is worthwhile considering the benefits they have asked for

3. Analyst-suggested functionality: No extra retraining should be required, unless users are absolutely convinced of benefits of extended functionality

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The Database Life Cycle (DBLC)

• Six phases:– Database initial

study– Database design– Implementation

and loading– Testing and

evaluation– Operation– Maintenance and

evolution

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Conceptual Design

• Creating a detailed, validated ERD• Independent of RDBMS chosen

DBMS Software Selection

• Critical to information system’s smooth operation

• Common factors affecting purchasing decisions:– Cost– DBMS features and tools– Underlying model– Portability– DBMS hardware requirements

• http://en.wikipedia.org/wiki/Comparison_of_relational_database_management_systems

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Logical Design

• Specifying the tables, attributes and keys

• Specifying the domain integrity and attribute constraints

• Dependent on chosen RDBMS

Physical Design

• Dependent on chosen hardware

Top-down versus bottom-updatabase design strategies• Top-down design

– Identifies groups of entities– Defines data elements for each of those groups

• Definition of different entity types • Definition of each entity’s attributes

• Bottom-up design – Identifies data attributes (items)– Groups them together into entities, and then larger groups

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Centralized vs. decentralized design• Centralized

design – When data

component is composed of small number of objects and procedures

– Typical of small systems

• Decentralized design – Data component has

large number of entities

– Complex relations on which complex operations are performed

– Problem is spread across several operational sites

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Sources

• Most of the slides are adapted from Database Systems: Design, Implementation and Management by Carlos Coronel and Steven Morris. 11th edition (2015) published by Cengage Learning. ISBN 13: 978-1-285-19614-5

• Other sources are noted on the slides themselves

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