1. Chapter 7 Selecting the Best Alternative Design Strategy
Essentials of Systems Analysis and Design Third Edition Joseph S. Valacich Joey F. George Jeffrey A. Hoffer
Chapter 7
Selecting the Best Alternative Design Strategy
7.1
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Learning Objectives
Learn to assemble the various pieces of an alternative design strategy.
Learn how to generate at least three alternative design strategies.
Discuss selecting the best design strategy using both qualitative and quantitative methods.
7.2
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3. Learning Objectives (continued)
Learn how to use the results of the analysis phase to update a Baseline Project Plan (BPP).
7.3
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4. Selecting the Best Alternative Design Strategy
Two basic steps:
Generate a comprehensive set of alternative design strategies
Select the one design strategy that is most likely to result in the desired information system
Process:
Divide requirements into different sets of capabilities
Enumerate different potential implementation environments that could be used to deliver the different sets of capabilities
Propose different ways to source or acquire the various sets of capabilities for the different implementation environments
7.4
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5. Selecting the Best Alternative Design Strategy(continued)
Deliverables
At least three substantially different system design strategies for building the replacement information system
A design strategy judged most likely to lead to the most desirable information system
A Baseline Project Plan (BPP) for turning the most likely design strategy into a working information system
7.5
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6. Generating Alternative Design Strategies
Best to generate three alternatives:
Low-End
Provides all required functionality users demand with a system that is minimally different from the current system
High-End
Solves problem in question and provides many extra features users desire
Midrange
Compromise of features of high-end alternative with frugality of low-end alternative
7.6
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7. Drawing Bounds on Alternative Designs
Minimum Requirements
Mandatory features versus desired features
Forms of features
Data
Outputs
Analyses
User expectations on accessibility, response time, and turnaround time
7.7
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8. Drawing Bounds on Alternative Designs (continued)
Constraints on System Development:
Time
Financial
Elements of current system that cannot change
Legal
Dynamics of the problem
7.8
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9. Criteria for Choosing Off-the-Shelf Software
Cost
In-house versus purchased
Functionality
Mandatory, essential, and desired features
Vendor Support
Installation
Training
Technical support
Viability of Vendor
7.9
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10. Criteria for Choosing Off-the-Shelf Software (continued)
Flexibility
Ease of customization
Documentation
User documentation
Technical documentation
Response Time
Ease of Installation
7.10
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7.11
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12. Validating Purchased Software Information
Information from Vendor
Software Evaluation Period
Customer References from Vendor
Independent Software Testing Service
Trade Publications
7.12
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13. Hardware and Software Issues
Existing Platform
Lower costs
Information system staff is familiar with operation and maintenance
Increased odds of successfully integrating system with existing applications
No added costs of converting old systems to new platform or transferring data
New Hardware and System Software
Some software components will only run on new platform
Developing system for new platform gives organization opportunity to upgrade technology holdings
New requirements may allow organization to radically change its computing operations
7.13
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14. Hardware and Software Issues (continued)
Request for Proposal (RFP)
A document provided to vendors to ask them to propose hardware and system software that will meet the requirements of your new system
7.14
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15. Implementation Issues
Technical and social aspects of implementation need to be addressed
Training
Disruption of Work
7.15
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16. Hoosier Burger’s New Inventory Control System
Replacement for existing system
Figure 7-4 ranks system requirements and constraints
7.16
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7.17
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18. Hoosier Burger’s New Inventory Control System (continued)
Figure 7-5 shows steps of current system
When proposing alternatives, the requirements and constraints must be considered
7.18
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7.19
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20. Hoosier Burger’s New Inventory Control System (continued)
Figure 7-7 lists 3 alternatives:
Alternative A is a low-end proposal
Alternative C is a high-end proposal
Alternative B is a midrange proposal
7.20
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21. Hoosier Burger’s New Inventory Control System (continued)
Selecting the Most Likely Alternative
Weighted approach can be used to compare the three alternatives
Figure 7-8 shows a weighted approach for Hoosier Burger
Left-hand side of table contains decision criteria
Constants and requirements
Weights are arrived at by discussion with analysis team, users, and managers
Each requirement and constraint is ranked
1 indicates that the alternative does not match the request well or that it violates the constraint
5 indicates that the alternative meets or exceeds requirements or clearly abides by the constraint
7.21
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7.22
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23. Hoosier Burger’s New Inventory Control System (continued)
Selecting the Most Likely Alternative
According to the weights used, alternative C appears to be the best choice
7.23
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24. Updating the Baseline Project Plan (BPP)
The Baseline Project Plan (BPP) was developed during systems planning and selection phase
Baseline Project Plan (BPP) can be used as an outline of a status report at analysis phase
Schedule will be updated to reflect actual activities and durations
An oral presentation of project status is typically made at this phase
7.24
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25. PVF WebStore: Selecting the Best Alternative Design Strategy
Requirements and constraints were compiled by consultant and team (see Table 7-4)
7.25
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7.26
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PVF WebStore: Selecting the Best Alternative Design Strategy (continued)
Proposed system is a scalable, three-tier approach
Scalable
The ability to seamlessly upgrade the system through either hardware upgrades, software upgrades or both
Three-tier
Web Server
Provides connection to the Internet and presentation of HTML page
Applications Server
Middle layer of software and hardware that lies between Web server and corporate network
Corporate network
Existing organizational computing infrastructure
7.27
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7.28
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29. Copyright 2006 Prentice-Hall, Inc.
Summary
Identify requirements and constraints
Generate alternative design strategies
Select the best design strategy
Update the Baseline Project Plan (BPP)
Select the best design strategy for Internet applications
7.29
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