1. Methodologies/Life Cycle Models

2. Some Advantages of a Methodology …
Ensures a consistent and repeatable process
Creates traceable projects
Enables better project communications
Makes projects more robust with respect to personnel changes
Enhances project troubleshooting and error-correcting
Improves accommodation of changes in requirements
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3. Some Standard Life Cycle Models
The Waterfall Model (Linear Sequential Model)
Prototyping Model
Rapid Application Development (RAD) Model
Evolutionary Development Models
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4. Waterfall Model
The Waterfall Model (Linear Sequential Model) is the de facto standard model
Uses distinct phases
Deliverables of one phase provide input for next phase
Walkthroughs and sign-offs at end of each phase
The BCBSSC methodology is based on the Waterfall Model
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5. Waterfall Model (cont’d)
Analysis
requirements
Design
program design
Code/ Test
coded and tested system
Delivery/
Maintenance
Implementation
Post-Implementation
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6. Prototyping Life Cycle Model
May be particularly useful when:
User interface is an important component of the product
User interface is particularly complex
Customer leaves interface design to systems analyst
Requirements appear to be somewhat in doubt, i.e. not fully agreed upon by customer(s)
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7. Prototyping as a Complete Life Cycle
Begin
Prototype Accepted
Complete Implementation
and Testing of
Production System
Determine
Requirements
& Design
repeat this cycle
Build Mockup
of System
Evaluate Mockup
With Customer
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8. Hybrid Prototyping/Waterfall Model
Analysis employing
prototyping
requirements
Design
This is the most frequent use for prototyping
program design
Code
tested system
Delivery/
Maintenance
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9. Prototyping: Pros and Cons
Integral involvement of the customer
More robust requirements
Great for refining user interfaces
Cons
Customers may have unrealistic expectations for a quick delivery of the final system
Not particularly applicable when complex processing algorithms or performance issues are important
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10. Hybrid Model May Be Very Useful ...
When user interface(s) are:
New
Complex
Not fully agreed upon by customer(s)
When customer:
Has a history of providing poorly thought out requirements
Has little experience in specifying requirements
Leaves interface design to systems analysts
Photo by larar
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11. Prototypes Can Reduce Surprises
Prototypes can help avoid customer surprises about:
User interfaces
Scope of the system
System work flow issues
How the problem is approached
Photo by Benjamin Earwicker
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12. RAD (Rapid Application Development)
Rapid Application Development (RAD) Model may be particularly applicable when:
Requirements are well understood and scope is tightly constrained
Reusable software components are available
System to be developed is highly modular
“High speed” adaptation of the Waterfall model
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13. RAD Characteristics
Requirements must be well understood and scope must be tightly constrained for RAD to be successful
RAD teams work in parallel “Waterfall” development teams
Best employed with highly modular systems
Photo by Kenneth De Buck
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14. Evolutionary Development Models
May be useful when:
Rapid development of incremental versions of the product seems desirable
Not all requirements are known at the beginning and the remaining requirements must be defined over a period of time
Developing “experimental products” in which design of later increments will depend on customer's acceptance of earlier increments
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15. Two Evolutionary Models
Incremental Model
Spiral Model
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16. Incremental Model Modified Waterfall model
Deliverable increments of the final product are produced sequentially
Phased delivery
Each phase delivers a usable product
Photo by N. Ghorn
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17. The Incremental Model -- Strategy
The first increment, or phase, is usually a “core” or high priority component/product
This core is delivered, evaluated, and used by the customer
Other components or phases are added incrementally
Can be used to “buy” time when budgets and/or schedule will not permit the delivery of the full system at one time
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18. Incremental Model -- An Example
Suppose our objective is to development a word processing
system. Using the Incremental model we might:
Develop basic file management, document creation, and editing functions as the first deliverable (the “core” product)
Refine the core and deliver more sophisticated editing capabilities in the second increment
Provide spell-checking in the third increment
Add page layout in the fourth increment
Each increment could be developed using a methodology based on the Waterfall model or the hybrid prototype/Waterfall model
© The KTP Company, 2005

19. Spiral Model
Couples iterative characteristic of prototyping with the incremental model
Rapid development of partially complete incremental versions of the product
Spiral stairway in a Vatican museum
Photo by Warren Gibb
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20. The Spiral Model -- Strategy
Product is developed in increments, but increments may be incomplete (prototypes, shells, etc.)
Increments are delivered, then evaluated for further development
More increments may be added as we learn more about what is required and what will be acceptable
© The KTP Company, 2005

21. Spiral Model Illustrated2
formulate
requirements 3 1
analyze needs
with customer
plan increment
modifications
finish/accept 4
start
design new
and modified
(more detailed)
increments
evaluate with
customer 6
build & release
next version 5
© The KTP Company, 2005

22. Group Exercise Take a moment or two to consider the following..
What are the strengths/weaknesses of the following models?
Waterfall
Hybrid waterfall/prototyping
RAD
Incremental
Spiral
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23. Team Activity #1
You’ve been assigned to lead the analysis for a new Web-based proof-of-concept project that will provide Web “front-end” access to your company’s traditionally mainframe-based applications.
This will be the company’s first foray into Web-based development.
The details of the new system requirements are still a bit sketchy, but management is convinced that such systems will become increasingly important for the future of the company. The company’s primary business is financial and investment services and one of the primary benefits management expects to realize is increased customer self-service and a subsequent reduction in costs of providing a subset of the company’s services.
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24. Team Activity #1 (cont’d)
Following are some essential features and high-level objectives for the proof-of-concept system.
The underlying philosophy for the system is one of customer self-service – a new approach for this company.
The system should provide customers direct access to status information appropriate to their current accounts.
The system should provide customers access to their account history with the company.
The system should provide “canned” responses for frequently asked questions about investment strategies.
The system should provide an opportunity for customers to pose additional questions (to be responded to later).
Identify what software life cycle model(s) you think might be appropriate for this project. Explain your choice(s).
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