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Sdlc

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Rishav Upreti
Rishav Upreti

The document discusses several software development life cycle (SDLC) models: the waterfall model, structured evolutionary prototyping, the incremental model, and the spiral model. The waterfall model involves sequential phases of requirements, design, implementation, and testing. Structured evolutionary prototyping uses iterative prototyping and user feedback to refine requirements. The incremental model delivers basic functionality early and evolves it over time. The spiral model incorporates risk analysis and prototyping into iterative waterfall cycles. Each model has strengths and weaknesses for different types of projects.

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Software Development Life Cycle (SDLC)
SDLC Model A framework that describes the activities performed at each stage of a software development project.
Waterfall Model Requirements defines needed information, function, behavior, performance and interfaces. Design data structures, software architecture, interface representations, algorithmic details. Implementation source code, database, user documentation, testing.
Waterfall Strengths Easy to understand, easy to use Provides structure to inexperienced staff Milestones are well understood Sets requirements stability Good for management control (plan, staff, track) Works well when quality is more important than cost or schedule
Waterfall Deficiencies All requirements must be known upfront Deliverables created for each phase are considered frozen inhibits flexibility Can give a false impression of progress Does not reflect problem-solving nature of software development iterations of phases Integration is one big bang at the end Little opportunity for customer to preview the system (until it may be too late)
Structured Evolutionary Prototyping Steps A preliminary project plan is developed An partial high-level paper model is created The model is source for a partial requirements specification A prototype is built with basic and critical attributes The designer builds the database user interface algorithmic functions The designer demonstrates the prototype, the user evaluates for problems and suggests improvements. This loop continues until the user is satisfied
Structured Evolutionary Prototyping Strengths Customers can see the system requirements as they are being gathered Developers learn from customers A more accurate end product Unexpected requirements accommodated Allows for flexible design and development Steady, visible signs of progress produced Interaction with the prototype stimulates awareness of additional needed functionality
Structured Evolutionary Prototyping Weaknesses Tendency to abandon structured program development for code-and-fix development Bad reputation for quick-and-dirty methods Overall maintainability may be overlooked The customer may want the prototype delivered. Process may continue forever (scope creep)
When to use the Incremental Model Risk, funding, schedule, program complexity, or need for early realization of benefits. Most of the requirements are known up-front but are expected to evolve over time A need to get basic functionality to the market early On projects which have lengthy development schedules On a project with new technology
Spiral SDLC Model Adds risk analysis, and prototyping to the waterfall model Each cycle involves the same sequence of steps as the waterfall process model
Spiral Quadrant Determine objectives, alternatives and constraints Objectives: functionality, performance, hardware/software interface, critical success factors, etc. Alternatives: build, reuse, buy, sub-contract, etc. Constraints: cost, schedule, interface, etc.
Spiral Quadrant Evaluate alternatives, identify and resolve risks Study alternatives relative to objectives and constraints Identify risks (lack of experience, new technology, tight schedules, poor process, etc. Resolve risks (evaluate if money could be lost by continuing system development
Spiral Quadrant Develop next-level product Typical activites: Create a design Review design Develop code Inspect code Test product
Spiral Quadrant Plan next phase Typical activities Develop project plan Develop configuration management plan Develop a test plan Develop an installation plan
Spiral Model Strengths Provides early indication of insurmountable risks, without much cost Users see the system early because of rapid prototyping tools Critical high-risk functions are developed first The design does not have to be perfect Users can be closely tied to all lifecycle steps Early and frequent feedback from users Cumulative costs assessed frequently
Spiral Model Weaknesses Time spent for evaluating risks too large for small or low-risk projects Time spent planning, resetting objectives, doing risk analysis and prototyping may be excessive The model is complex Risk assessment expertise is required Spiral may continue indefinitely Developers must be reassigned during non-development phase activities May be hard to define objective, verifiable milestones that indicate readiness to proceed through the next iteration
When to use Spiral Model When creation of a prototype is appropriate When costs and risk evaluation is important For medium to high-risk projects Long-term project commitment unwise because of potential changes to economic priorities Users are unsure of their needs Requirements are complex New product line Significant changes are expected (research and exploration)

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Sdlc

  • 2. SDLC Model A framework that describes the activities performed at each stage of a software development project.
  • 3. Waterfall Model Requirements defines needed information, function, behavior, performance and interfaces. Design data structures, software architecture, interface representations, algorithmic details. Implementation source code, database, user documentation, testing.
  • 4. Waterfall Strengths Easy to understand, easy to use Provides structure to inexperienced staff Milestones are well understood Sets requirements stability Good for management control (plan, staff, track) Works well when quality is more important than cost or schedule
  • 5. Waterfall Deficiencies All requirements must be known upfront Deliverables created for each phase are considered frozen inhibits flexibility Can give a false impression of progress Does not reflect problem-solving nature of software development iterations of phases Integration is one big bang at the end Little opportunity for customer to preview the system (until it may be too late)
  • 6. Structured Evolutionary Prototyping Steps A preliminary project plan is developed An partial high-level paper model is created The model is source for a partial requirements specification A prototype is built with basic and critical attributes The designer builds the database user interface algorithmic functions The designer demonstrates the prototype, the user evaluates for problems and suggests improvements. This loop continues until the user is satisfied
  • 7. Structured Evolutionary Prototyping Strengths Customers can see the system requirements as they are being gathered Developers learn from customers A more accurate end product Unexpected requirements accommodated Allows for flexible design and development Steady, visible signs of progress produced Interaction with the prototype stimulates awareness of additional needed functionality
  • 8. Structured Evolutionary Prototyping Weaknesses Tendency to abandon structured program development for code-and-fix development Bad reputation for quick-and-dirty methods Overall maintainability may be overlooked The customer may want the prototype delivered. Process may continue forever (scope creep)
  • 9. When to use the Incremental Model Risk, funding, schedule, program complexity, or need for early realization of benefits. Most of the requirements are known up-front but are expected to evolve over time A need to get basic functionality to the market early On projects which have lengthy development schedules On a project with new technology
  • 10. Spiral SDLC Model Adds risk analysis, and prototyping to the waterfall model Each cycle involves the same sequence of steps as the waterfall process model
  • 11. Spiral Quadrant Determine objectives, alternatives and constraints Objectives: functionality, performance, hardware/software interface, critical success factors, etc. Alternatives: build, reuse, buy, sub-contract, etc. Constraints: cost, schedule, interface, etc.
  • 12. Spiral Quadrant Evaluate alternatives, identify and resolve risks Study alternatives relative to objectives and constraints Identify risks (lack of experience, new technology, tight schedules, poor process, etc. Resolve risks (evaluate if money could be lost by continuing system development
  • 13. Spiral Quadrant Develop next-level product Typical activites: Create a design Review design Develop code Inspect code Test product
  • 14. Spiral Quadrant Plan next phase Typical activities Develop project plan Develop configuration management plan Develop a test plan Develop an installation plan
  • 15. Spiral Model Strengths Provides early indication of insurmountable risks, without much cost Users see the system early because of rapid prototyping tools Critical high-risk functions are developed first The design does not have to be perfect Users can be closely tied to all lifecycle steps Early and frequent feedback from users Cumulative costs assessed frequently
  • 16. Spiral Model Weaknesses Time spent for evaluating risks too large for small or low-risk projects Time spent planning, resetting objectives, doing risk analysis and prototyping may be excessive The model is complex Risk assessment expertise is required Spiral may continue indefinitely Developers must be reassigned during non-development phase activities May be hard to define objective, verifiable milestones that indicate readiness to proceed through the next iteration
  • 17. When to use Spiral Model When creation of a prototype is appropriate When costs and risk evaluation is important For medium to high-risk projects Long-term project commitment unwise because of potential changes to economic priorities Users are unsure of their needs Requirements are complex New product line Significant changes are expected (research and exploration)