Transcript Chapter 9 review

Database Systems:
Design, Implementation, and
Management
Chapter 9
Database 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
Entire SDLC
BTM Minor
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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 one
2. User-requested functionality: The system should add new features
required by users
3. 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:
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Cost
DBMS features and tools
Underlying model
Portability
DBMS hardware requirements
• http://en.wikipedia.org/wiki/Comparison_of_re
lational_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-up
database 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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