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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