CSC426 - SDLC Models
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This lecture note discusses software development process models. It begins by defining the software development process and outlining its key activities: specification, development, validation, and evolution. It then examines six common software development life cycle models - waterfall, evolutionary, V-shaped, spiral, agile, and rational unified process. For each model, it provides an overview and diagram of the process, discusses strengths and weaknesses, and compares it with other models. The note aims to educate students on established frameworks for developing software.
CSC426 - SDLC Models
- 1. CSC 426 (Software Engineering) Lecture Note Part I Cont’d: SOFTWARE DEVELOPMENT PROCESS MODELS AJAYI, Olusola Olajide Department of Computer Science, Faculty of Science, Adekunle Ajasin University, Akungba-Akoko, Ondo State, Nigeria. [email protected] / [email protected] 08113699553 / 07056433798 / 08137044500
- 2. Software Development Process (SDP)_ •Munassar et al (2010) defined it as an abstract representation of a process that presents a description of a process from some particular perspectives. •In this class/study, SDP refers to activities involved in producing/developing software.
- 3. SDP Cont’d – The Activities/Processes Software Specification Software Development Software Validation Software Evolution
- 4. SDP Cont’d – The Activities/Processes Software Specification Software Development Software Validation Software Evolution Figure 1: Software Development Activities/Processes
- 5. SDP Activities/Processes – The Breakdown •Software Specification: This activity involves stating the functionalities (operations) as well as the constraints/limitations of the software. Major Activity Requirements. •Software Development: This activity involves developing (producing) a software according to the specification outlined in the first stage of the development process. Major Activity Designs.
- 6. SDP Activities/Processes – The Breakdown Cont’d •Software Validation: This activity checks the software developed to ensure it conforms to the specification earlier concluded upon. Major Activity Testing. •Software Evolution: This activity ensures that the software produced is modifiable/adjustable. Major Activity Maintenance.
- 7. SDP Activities/Processes – The Breakdown Cont’d •Paraphrasing Pressman, R. S. (2010), we can define SD Process as a roadmap to defining, building, testing, & deploying timely and high quality software applications. Both User & Developers are involved Only Development Team are involved Only Development Team are involved Both User & Developers are involved Requirements Designs Testing Maintenance
- 8. SDLC Models •This refers to the existing and established frameworks for developing software. •For the purpose of this study, we shall be examining six (6) common ones.
- 9. SDLC Models Cont’d i. Waterfall Model ii. Evolutionary Model iii. V-Shape Model iv. Spiral Model v. Agile Development Model vi. Rational Unified Process (RUP) Model
- 10. SDLC Models Cont’d i. Waterfall Model Undoubtedly the oldest and famous of all the available models. It acts as baseline for other SDLC models. In other words, other models are derivatives of Waterfall Model. It major strength lies in the fact that it dwells much on requirement gathering and ascertaining of same (by way of feedbacks) to prevent flaws in the development of the project. Most suitable where requirement is well understood.
- 11. SDLC Models Cont’d i. Waterfall Model - VARIANTS Requirement Analysis and Definition/Specification Implementation and Unit Testing Integration and System Testing Operation and Maintenance System and Software Design Figure 2: Classical Waterfall Model
- 12. SDLC Models Cont’d i. Waterfall Model – VARIANTS cont’d Figure 3: Pure Waterfall Model
- 13. SDLC Models Cont’d i. Waterfall Model – STRENGTHS/ADVANTAGES With her ‘define-b4-design’ & ‘design-b4-coding’ approach, it reduces flaws/errors in development. Applications developed with it, are easily understood, implementable and maintained. Documentation is embraced and enhanced. With its deep flow, quality assurance is ensured.
- 14. SDLC Models Cont’d i. Waterfall Model – WEAKNESSES/DISADVANTAGES Costly Time-consuming, leading to late project delivery
- 15. Maintenance SDLC Models Cont’d i. Waterfall Model – SUMMARY Summarily, Waterfall Model complies with the process flow shown below: Require ments Desig ns Testing Figure 4: SDLC Process showing Waterfall Compliance Compliance
- 16. SDLC Models Cont’d ii. Evolutionary Model This model involves the culmination of major activities involved in developing software. The model emphasize ‘fast/quick’ design approach to solution development. Unlike Waterfall, the strength of this model is time-saving, which is achieved by rapid way of developing software with adequate feedbacks.
- 17. SDLC Models Cont’d ii. Evolutionary Model - VARIANTS The available variants include: Throw-Away Prototyping Model Rapid Application Development Model / Iterative Prototyping Model Incremental Prototyping Model
- 18. SDLC Models Cont’d a. Throwaway Prototyping Model – Emphasizes fast design + minimal requirement analysis. In this prototyping type, a small portion of an ‘on- going’ system is given to the client/user for evaluation purpose. The feedbacks allow for some modifications to be carried out on the main system, after which the prototype is discarded/done with/thrown away. This is why it is also refer to as a working system – it is only developed for evaluation/testing purposes, it is never part of the final delivered system/software.
- 19. SDLC Models Cont’d Figure 5: Throwaway Prototyping Model – Variant I Requirement Analysis Design/Build Demo Software Testing (Customer Test Run Demo App)
- 20. SDLC Models Cont’d Figure 6: Throwaway Prototyping Model – Variant II
- 21. SDLC Models Cont’d b. Rapid Application Development (RAD) This iterative model emphasizes component- based construction in rapid software development approach. It embraces, encourages and enables participation of development team in actualizing speedy/timely development. Figure 7 shows the different phases of RAD / Iterative model as catered by different development teams.
- 22. SDLC Models Cont’d Figure 7: RAD Model – Variant I
- 23. SDLC Models Cont’d Figure 8: RAD Model – Variant II
- 24. SDLC Models Cont’d Figure 9: RAD Model – Variant III Specificatio n Validation Developmen t Initial Version Intermediate Version Final Version Specification Development Validation 1st Version Intermediate Version Final Version or Product
- 25. SDLC Models Cont’d Figure 10: RAD Model – Variant IV Requirement Analysis Develop Prototype DeploymentClient/User Evaluation Feedback for Modification Final Implementation & Integration Deployment & Operation Maintenance
- 26. SDLC Models Cont’d c. Incremental Model – Like the Prototyping, it emphasizes fast design + minimal requirement analysis. However unlike prototyping where the demo app is delivered, the core product/app is delivered, used and reviewed by the user, and feedback for modifications. Figure 11 shows the Incremental Model.
- 27. SDLC Models Cont’d Figure 11: Incremental Model
- 28. SDLC Models Cont’d Differences between Waterfall & Evolutionary Waterfall Evolutionary Time consuming Time-saving Costly Cheap Inflexible Flexible Process is easily understood, implementable, and maintainable Clumsy process due to excessive iterations and prototypes Sufficient requirement analysis carried out Insufficient requirement analysis performed Table 1: Differences between Waterfall and Evolutionary Models
- 29. SDLC Models Cont’d iii. V-Shaped Model This is an extension of the Waterfall Model, whose development is bent upward after the implementation/coding phase to form a V-Shape. Figure 12 shows this.
- 30. SDLC Models Cont’d i. V-Shaped Model Figure 12: V-Shaped Model
- 31. SDLC Models Cont’d i. V-Shaped Model – STRENGTHS/ADVANTAGES Like the Waterfall, it is easy to understood, implement and maintain. Most suitable for use where requirements are clearly spelt out. Each development phase and the technologies/tools involved, are known.
- 32. SDLC Models Cont’d i. V-Shaped Model – WEAKNESSES/DISADVANTAGES Again, like the Waterfall Model, it is inflexible Costly Time-consuming (even more than the Waterfall Model). Why?
- 33. SDLC Models Cont’d Differences between Waterfall & V-Shaped Waterfall V-Shaped No planning at early stage – jump start to requirement. Planning is done as early test approach. Table 2: Differences between Waterfall and V-Shaped Models
- 34. SDLC Models Cont’d iv. Spiral Model This combines the features/characteristics and strengths of prototyping and waterfall models in tandem with adequate risk analysis. It is most suitable for large, complex and security- driven/risk-involving software projects. It was described and presented by Barry Boehm in 1986 in his paper, titled: ‘A Spiral Model of Software Development and Enhancement’. It was widely accepted not because it discusses iterative processes of developing software like other models but because it presented the necessity for risk pattern and cost to be examined from the requirement to the development/deployment stage.
- 35. SDLC Models Cont’d iv. Spiral Model Figure 13: Spiral Model – A Typical Model, Variant I
- 36. SDLC Models Cont’d iv. Spiral Model Figure 14: Spiral Model – A Typical Model, Variant II
- 37. SDLC Models Cont’d iv. Spiral Model Figure 15: Spiral Model – A Full/Complete Model, Variant I
- 38. SDLC Models Cont’d iv. Spiral Model Figure 16: Spiral Model – A Full/Complete Model, Variant II
- 39. SDLC Models Cont’d iv. Spiral Model – Phases & Activities (1) OBJECTIVE/PLANNING Phase i. Decide on the visibility/possibility of the project. ii. Determine the cost of implementation. iii. Specify project timeline. iv. Suggest alternative approach to implementation.
- 40. SDLC Models Cont’d iv. Spiral Model – Phases & Activities (2) RISK ASSESSMENT/ANALYSIS Phase What do we look out for? What do we analyze? i. Developer’s level of experience. ii. Requirement information. iii. Delivery schedules. iv. Key system operations.
- 41. SDLC Models Cont’d iv. Spiral Model – TAXONOMY (1) Risk: Implies an uncertain outcome that has potentials for loss. It refers to measurable parameter that determines loss. (2) Verification: Implies checks to ensure the team is building the software product rightly. (3) Validation: Implies checks to ensure the team is building the right software product. (4) Testing: Implies executing the program/application with set of data (valid & invalid) to study the software behavior. (5) Debugging: Implies examining code(s) that cause(s) failing in software performance.
- 42. SDLC Models Cont’d iv. Spiral Model Flowchart Figure 17: Spiral Model – The Flow
- 43. SDLC Models Cont’d iv. Spiral Model – STRENGTHS/ADVANTAGES Risk avoidance. Precise knowledge of requirements. Accommodates frequent changes in requirements. Like Waterfall, it is more realistic than other iterative models in that it allows software product to evolve as the development process progresses.
- 44. SDLC Models Cont’d iv. Spiral Model – WEAKNESSES/DISADVANTAGES Time consuming. Not generic in application – Different application with different risk factors; so, it has to be developed and applied differently. Complex process. Involve excessive and rigorous documentation process. Unsuitable for small software projects.
- 45. SDLC Models Cont’d Differences between Waterfall & Spiral Waterfall Spiral Risk is not considered Analyzes and manages risk No adequate estimation of budget Adequate estimation of budget achieved through planning and progressive phases Costly Costlier Table 3: Differences between Waterfall and Spiral Models
- 46. SDLC Models Cont’d Spiral Model – Boehm’s Philosophy Figure 18: Boehm’s Philosophy that prompted Spiral Model “Stop the life cycle—I want to get off!” “Life-cycle Concept Considered Harmful.” “The waterfall model is dead.” “No, it isn’t, but it should be.”
- 47. SDLC Models Under Topic Exercise (UTE) 1 i. Following the demonstrated discussion pattern of this course and particularly under this topic, write on: a. Agile Model b. RUP Model ii. Enumerate the strengths and weaknesses of the various Evolutionary Models. iii. Come up with a modified Spiral Model and discuss the activities of each phase of the model. iv. In few paragraphs and in convincing ways, discuss the necessities and benefits of modeling as a pointer and preceding step to software development.
- 48. SDLC Models Under Topic Exercise (UTE) 2 i. Iterative vs Incremental Models – Comment on the ‘fight’. ii. Discuss the differences between: i. Evolutionary and V-Shaped Models ii. Evolutionary and Spiral Models iii. Evolutionary and Agile Models iv. Evolutionary and RUP Models iii. Between V-Shaped and Agile Models, which will you prefer and why? iv. V-Shaped and Agile: Which is more agile? Discuss. v. Considering Spiral and Agile Models, which springs up software faster and more reliably? Lecture a fellow.