Waterfall with Prototyping

Prototyping to analysis and design phases

• Preview and validation of User Interface by customer.
• Preview and validation of complex workflows by customer.
• Technical risks mitigation etc. Feasibility.

  Biggest Risks

• Correctness and completeness of earlier phases is a prerequisite of each phase.
• Risks related to complex functionalities and large size of projects.
• Might not handle all scenarios.

Evolutionary Prototyping Methodology.

1. Here the system concept evolves during the project
   • Develop a prototype
   • Show it to customer. Get their feedback.
   • Refine the prototype. Repeat till prototype is “good”.
   • Complete any pending work and release the product.
2. Appropriate when
   • Rapidly changing requirements
   • Customer can not commit to a set of requirements. Poor understanding of the application area (by customer or developer).
   • Poor understanding of technology, architecture or algorithms.
3. Problems
   • Cant predict efforts, size, costs.
   • Demands on good engineering, to ensure sustaining every iteration.

Rapid Application Development

1. Modified waterfall model that emphasizes an extremely short development life cycle
   • Methodology driven by tools which achieve rapid development
     • Joint Requirements Planning
     • Joint Application Development
     • Construction
     • Cutover
   • Costs of rework is very less. So, design and testing phases and shortened
2. Appropriate if the requirements can be realized using the tools
   • CASE tools (such as VB, Borland Delphi, PowerBuilder etc.)

Product Lifecycle Models

1. Modification of iterative model
   • Multiple cycles of development, adding newer features in every cycle.
   • Requirements driven by the market, not by specific customers.
     • Influenced by competing products.
     • Present customer base as well as targeted customers.
2. Each cycle builds on earlier cycle’s work products
   • Stable architecture and standard development practices.
   • Requirements gathering and analysis is more tedious.
   • HLD and architecture inherited from earlier cycles.
   • DD & CUT combined to one stage.
   • System testing is elaborate.
   • Customer testing is more tedious: alpha and beta.
3. Biggest Risks and Challenges
   • Conflicting requirements from diverse customer base.
   • Need to rapidly change to adapt to changing market pressures.