Software process models shaukat wasi
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The document discusses various software process models, emphasizing the need for organized approaches to software development to address inadequacies in scheduling, quality, and user satisfaction. It covers models such as the Waterfall, V-Model, Incremental, Evolutionary, and Agile methodologies, highlighting their characteristics, advantages, and limitations. The summary also introduces concepts like iterative and incremental development, the importance of user requirements, and the principles of Agile as outlined in the Agile Manifesto.
Software process models shaukat wasi
- 1. Software Process Models Spring 2020 Shaukat Wasi Some slides taken from Roddy
- 2. Level 1 – Ad Hoc
- 3. Code & Fix • The earliest approach • Write code • Fix it to eliminate any errors that have been detected, to enhance existing functionality, or to add new features • Source of difficulties and deficiencies – impossible to predict – impossible to manage
- 4. Models are needed • Symptoms of inadequacy: the software crisis – scheduled time and cost exceeded – user expectations not met – poor quality • The size and economic value of software applications required appropriate "process models"
- 5. Process model goals (B. Boehm 1988) “Determine the order of stages involved in software development and evolution, and to establish the transition criteria for progressing from one stage to the next. …. Thus a process model addresses the following software project questions: – What shall we do next? – How long shall we continue to do it?"
- 6. Software Process Model Attempt to organize the software life cycle by • defining activities involved in software production • order of activities and their relationships Goals of a software process – standardization, predictability, productivity, high product quality, ability to plan time and budget requirements
- 7. Software Process model with Umbrella Activities
- 8. Choosing a Software Process Model
- 9. Process as a "black box" Product Informal Requirements Process
- 10. Process as a "white box" Product Informal Requirements Process feedback
- 11. Waterfall Model
- 12. Waterfall model • Invented in the late 1950s for large air defense systems, popularized in the 1970s • They organize activities in a sequential flow • Exist in many variants, all sharing sequential flow style
- 14. Critical evaluation of the waterfall model + software process subject to discipline, planning, and management + postpone implementation to after understanding objectives – linear, rigid, monolithic – no feedback – no parallelism – a single delivery date
- 15. Problems with waterfall • Estimates made when limited knowledge available • Difficult to gather all requirements once and for all – users may not know what they want – requirements cannot be frozen
- 16. Best Suited for: Mission Critical Projects No choice for errors Well defined Requirements NOT Time critical
- 17. V Model
- 18. Waterfall model variation – V Model
- 19. V and V Combined Verification In the concept of verification in the V-Model, static analysis technique is carried out without executing the code. This evaluation procedure is carried out at the time of development to check whether specific requirements will meet or not. Validation This concept of V-Model comprises of dynamic analysis practice (both functional as well as non-functional), and testing is done by code execution. The validation of a product is done once the development is complete for determining if the software meets up the customer hope needs. So both verification and validation are combined and work in parallel to make the V-Model fully functional.
- 21. Increment? • Increment refers to the quantifiable outcome of each iteration • Increment has the obvious implication that there should be more of something at the end of an iteration than there was at the start. • Incremental development is a staging and scheduling strategy ‘’in which the various parts of the system are developed at different times or rates, and integrated as they are completed.’’
- 22. Iteration? • Iteration refers to the cyclic nature of a process in which activities are repeated in a structured manner. • Iterative development is a rework scheduling strategy ‘’in which time is set aside to revise and improve parts of the system.’’
- 23. Iterative and incremental Product vs Process: • Incremental fundamentally means add onto. Incremental development helps you improve your process. • Iterative fundamentally means re-do. Iterative development helps you improve your product. In Code: while ( project.isRunning() ) { project.bugsFixed++; project.featuresComplete++; }
- 25. Incremental development • Rather than deliver the system as a single delivery, the development and delivery is broken down into increments with each increment delivering part of the required functionality • User requirements are prioritised and the highest priority requirements are included in early increments • Once the development of an increment is started, the requirements are frozen though requirements for later increments can continue to evolve
- 27. Evolutionary Models Iterative + Incremental Usually a set of core product or system requirements is well understood, but the details and extension have yet to be defined. It is iterative that enables you to develop increasingly more complete version of the software i.e. evolution of software. Two Types: Prototyping and Spiral
- 30. Spiral Model
- 31. Spiral Model Iterative (multiple passes over the circuits) + Incremental (Each circuit adds next level to development) + Risk Driven Based on Water fall model (Same steps in sequence) The first circuit in the clockwise direction might result in the product specification; subsequent passes around the spiral might be used to develop a prototype and then progressively more sophisticated versions of the software. Each pass results in adjustments to the project plan. Cost and schedule are adjusted based on feedback. Also, the number of iterations will be adjusted by project manager.
- 32. 3 Concerns on Evolutionary Processes 1. Planning is at Risk in prototyping model due to uncertain no: of cycles required to reach the final product. 2. Development speed is some what slow as the iterations need time to cover the improvements. Hence being too fast will bring the process to chaos and being too slow will effect the productivity. 3. High Quality VS Timely delivery tradeoff. Iterations do improve but to what extent iterations are to be added is a question.
- 33. Unified Process Modeling (UPM)
- 34. Unified Process Model (UPM) Integrating two seemingly contradicting insights: Definitive activities and deliverables as in the Waterfall Model. Iterative and incremental processes. A project is split into several phases: Each phase is split into several iterations. Each iteration consists of the traditional process activities, known as workflow. Each workflow places different emphasis on the activities depending on the current iteration.
- 38. Work together!
- 39. Agile Manifesto “We are uncovering better ways of developing software by doing it and helping others do it. Through this work we have come to value: •Individuals and interactions over processes and tools •Working software over comprehensive documentation •Customer collaboration over contract negotiation •Responding to change over following a plan That is, while there is value in the items on the right, we value the items on the left more.” Kent Beck et al
- 40. Scrum • Focus on software development without defining phases and workproducts, only focus on increments through sprints • “Getting things done” • Roles: – Scrum Master – Product Owner – Team member • Especially useful for experienced developers
- 41. Scrum
- 42. Scrum
- 43. Kanban Similar to Scrum but Priority Based instead of Time Based
- 46. Extreme Programming – Top Principles
- 48. Selection criteria for lifecycle models
- 49. Conclusion
- 51. Choosing a Software Process Model