Software Process Model
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This document discusses different software process models including waterfall, prototyping, incremental development, spiral, RAD, and V-models. It explains the key stages and benefits and limitations of each model. The document emphasizes that each model tries to provide a framework for software development but that borrowing from multiple models may be necessary. Real-life examples like Windows development are given to illustrate using the spiral model.
Software Process Model
- 1. CSE 2205 Software Engineering Md. Shafiuzzaman Lecture #2
- 2. Today • The Software Process Model
- 7. Why have a model • A model recognize that Software Engineering is more than just programming • Recognize product life cycles – Various requirements specification phases – Design phases – Coding and testing phases – Maintenance phase (bug fixes and revisions)
- 8. More reasons to have a model • A model helps recognize and define the division of labor – Individual responsibilities (program managers, software design engineers, UI designers, testers, product support, internationalization, marketing, etc.) – How big should a team be – Parallel work efforts – Does a one person team need a model • Provide a common means of communication between all involved parties • Documentation is vital – Comments in the code is not sufficient documentation
- 9. Goals of a good model • The obvious “Provide a framework for building a solidly engineered product” • A paradigm that adds discipline and order to software development • Provides a formal mechanism to clarify, track, and modify the product requirements throughout the product life cycle • Provide a guideline for engineers to use in the product life cycle • Provide feedback into the development cycle
- 10. More goals of a good model • Compel engineers to want to use it – Doesn’t get in the way – Convinces them that they will build a better product – Be easy to understand and use • Keep everyone organized • Many more “common sense” reasons
- 12. First a simple model (waterfall)
- 13. More on the waterfall model • What it is – Each phase is carried out completely (for all requirements) before proceeding to the next – The process is strictly sequential - no backing up or repeating phases • What it tried to accomplish – Account for more than programming – Feedback between phases – A requirement change can have a major cost downstream
- 14. More on the waterfall model • Benefits – Simple, easy to understand and follow – Highly structured, therefore good for beginners – After specification is complete, low customer involvement required • Limitations – Limited feedback increases risk – Inflexible - can't adapt to changes in requirements – A requirement change can have a major cost downstream
- 16. More on prototyping model • A variation of the waterfall that adds a new phase, prototyping • Prototypes intend to reduce risk by building a quick and dirty replica or mockup of the intended system. • Demonstrate technical feasibility when the technical risk is high. • Used to better understand and elicit user requirements. • Goal: reduce risk and limit costs by increasing understanding of proposed solutions before committing more resources.
- 18. More on incremental development • developing an initial implementation • exposing this to user feedback • evolving it through several versions until an acceptable system has been developed.
- 19. Incremental Vs Waterfall Model • cost of accommodating changing • customer feedback • rapid delivery
- 21. More on the spiral model • What it is – An iterative approach where multiple passes are made through each phase – During each iteration the system is explored at greater depth and more detail is added • What it tried to accomplish – Recognize that Software Engineering is a process of iterative refinement – Allow for alternate designs and implementations
- 22. More on the spiral model • Benefits – The iterative natures allows for knowledge gained during early passes to inform subsequent passes – Requires low up-front commitment – Manages uncertainty inherent in exploratory projects – Strong approval and documentation control – Additional Functionality can be added at a later date – Software is produced early in the software life cycle
- 23. More on the spiral model • Limitations – Difficult to establish stable documents – Things keep getting modified during each iteration – Too much dependable on Risk Analysis and requires highly specific expertise – Spiral may go on indefinitely – End of the project may not be known early – May be hard to define objective, verifiable milestones – Large numbers of intermediate stages require excessive documentation
- 24. When to use Spiral model • When costs and risk evaluation is important • For medium to high-risk projects • Users are unsure of their needs • Requirements are complex • New product line • Significant changes are expected (research and exploration)
- 25. Real Life Examples of software using spiral model • Evolution of Microsoft Windows operating system
- 26. SDLC Models
- 27. Assignments • RAD model (Odd Roll Numbers) • V-Model (Even Roll Numbers) • Instructions: – Explain its distinction with others – Benefits & Limitations – Where to use – Real life examples
- 28. Next Class • Iterative Model • Agile
- 29. Lessons from the models • Each trying to capture or dictate how a project should be run • Even a good properly applied model cannot fix a flawed design • Not any model offers the 100% solution • Often borrowing from one or more model is necessary • Just as Software Engineering is full of compromises so is using a Software Engineering model • So take these models with a grain of salt and use only those parts that apply to your situation