Sdlc process models in software engineering basics by ram k paliwal
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1) Prescriptive process models were proposed to structure software development but software engineering remains complex. 2) Different process models apply different emphases to core framework activities and define different process flows. 3) The waterfall model is a sequential approach dividing the lifecycle into phases that do not overlap. It is simple but inflexible to changes.
Sdlc process models in software engineering basics by ram k paliwal
- 1. Software Engineering- Unit 1 SOFTWARE DEVELOPMENT LIFE CYCLE PROCESS MODEL AND CHARACTERISTICS IN SOFTWARE ENGINEERING BY RAM K PALIWAL 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 1
- 2. Process Models Prescriptive process models were originally proposed to bring order to the chaos of software development. History has indicated that these traditional models have brought a certain amount of useful structure to software engineering work and have provided a reasonably effective road map for software teams. However, software engineering work and the product that it produces remain on “the edge of chaos.” All software process models can accommodate the generic framework activities, but each applies a different emphasis to these activities and defines a process flow that invokes each framework activity (as well as software engineering actions and tasks) in a different manner 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 2
- 3. Software Development Models Waterfall Model The waterfall model, sometimes called the classic life cycle, suggests a systematic, sequential approach. Classical waterfall model divides the life cycle into a set of phases. This model considers that one phase can be started after completion of the previous phase. That is the output of one phase will be the input to the next phase. Here the phases do not overlap with each other. The different sequential phases of the classical waterfall model are shown in the figure: 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 3
- 4. Waterfall Model 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 4
- 5. Waterfall Model Feasibility Study: The main goal of this phase is to determine whether it would be financially and technically feasible to develop the software. Requirements analysis and specification: The aim of the requirement analysis and specification phase is to understand the exact requirements of the customer and document them properly. This phase consists of two different activities. ◦ Requirement gathering and analysis ◦ Requirement specification 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 5
- 6. Waterfall Model Design: The aim of the design phase is to transform the requirements specified in the SRS document into a structure that is suitable for implementation in some programming language. Coding and Unit testing: In coding phase software design is translated into source code using any suitable programming language. Thus each designed module is coded. The aim of the unit testing phase is to check whether each module is working properly or not. 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 6
- 7. Waterfall Model Integration and System testing: Integration of different modules are undertaken soon after they have been coded and unit tested. Integration of various modules is carried out incrementally over a number of steps. System testing consists three different kinds of testing activities as described below: ◦ α-testing ◦ β-testing ◦ Acceptance testing 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 7
- 8. Waterfall Model Maintenance: Maintenance is the most important phase of a software life cycle. The effort spent on maintenance is the 60% of the total effort spent to develop a full software. There are basically three types of maintenance: ◦ Corrective Maintenance ◦ Perfective Maintenance ◦ Adaptive Maintenance 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 8
- 9. Waterfall Model Advantages 1. This model is very simple and is easy to understand. 2. Phases in this model are processed one at a time. 3. Each stage in the model is clearly defined. 4. This model has very clear and well understood milestones. 5. Process, actions and results are very well documented. 6. Reinforces good habits: define-before- design, design-before-code. 7. This model works well for smaller projects and projects where requirements are well understood. 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 9
- 10. Waterfall Model Disadvantages Classical waterfall model suffers from various shortcomings, basically we can’t use it in real projects, but we use other software development lifecycle models which are based on the classical waterfall model. Below are some major drawbacks of this model: ◦ No feedback path ◦ Difficult to accommodate change requests ◦ No overlapping of phases 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 10
- 11. Prototyping Model Prototyping is defined as the process of developing a working replication of a product or system that has to be engineered. 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 11
- 12. Prototyping Model In this process model, ◦ The system is partially implemented before or during the analysis phase thereby giving the customers an opportunity to see the product early in the life cycle. ◦ The process starts by interviewing the customers and developing the incomplete high-level paper model. ◦ This document is used to build the initial prototype supporting only the basic functionality as desired by the customer. ◦ Once the customer figures out the problems, the prototype is further refined to eliminate them. ◦ The process continues till the user approves the prototype and finds the working model to be satisfactory. 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 12
- 13. Prototyping Model There are 2 approaches for this model: Rapid Throwaway Prototyping ◦ This technique offers a useful method of exploring ideas and getting customer feedback for each of them. Evolutionary Prototyping ◦ In this method, the prototype developed initially is incrementally refined on the basis of customer feedback till it finally gets accepted. 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 13
- 14. Rapid Throwaway Prototyping Model 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 14
- 15. Evolutionary Prototyping Model 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 15
- 16. Prototyping Model Advantages – 1. The customers get to see the partial product early in the life cycle. This ensures a greater level of customer satisfaction and comfort. 2. New requirements can be easily accommodated as there is scope for refinement. 3. Missing functionalities can be easily figured out. 4. Errors can be detected much earlier thereby saving a lot of effort and cost, besides enhancing the quality of the software. 5. The developed prototype can be reused by the developer for more complicated projects in the future. 6. Flexibility in design. 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 16
- 17. Prototyping Model Disadvantages – 1. Costly with respect to time as well as money. 2. There may be too much variation in requirements each time the prototype is evaluated by the customer. 3. Poor Documentation due to continuously changing customer requirements. 4. It is very difficult for the developers to accommodate all the changes demanded by the customer. 5. There is uncertainty in determining the number of iterations that would be required before the prototype is finally accepted by the customer. 6. After seeing an early prototype, the customers sometimes demand the actual product to be delivered soon. 7. Developers in a hurry to build prototypes may end up with sub-optimal solutions. 8. The customer might lose interest in the product if he/she is not satisfied with the initial prototype. 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 17
- 18. References: https://www.geeksforgeeks.org/software-engineering-software-crisis/ 7th edition Software Engineering A Practitioners Approach by Roger S. Pressman 8/20/2019 RAM K PALIWAL - SOFTWARE PROCESS IN SOFTWARE ENGINEERING - UNIT 1 18
Editor's Notes
- #6: The feasibility study involves understanding the problem and then determine the various possible strategies to solve the problem. These different identified solutions are analyzed based on their benefits and drawbacks, The best solution is chosen and all the other phases are carried out as per this solution strategy. Requirement gathering and analysis: Firstly all the requirements regarding the software are gathered from the customer and then the gathered requirements are analyzed. The goal of the analysis part is to remove incompleteness (an incomplete requirement is one in which some parts of the actual requirements have been omitted) and inconsistencies (inconsistent requirement is one in which some part of the requirement contradicts with some other part). Requirement specification: These analyzed requirements are documented in a software requirement specification (SRS) document. SRS document serves as a contract between development team and customers. Any future dispute between the customers and the developers can be settled by examining the SRS document.
- #8: During each integration step, previously planned modules are added to the partially integrated system and the resultant system is tested. Finally, after all the modules have been successfully integrated and tested, the full working system is obtained and system testing is carried out on this. α-testing: α-testing is the system testing performed by the development team. β-testing: β-testing is the system testing performed by a friendly set of customers. Acceptance testing: After the software has been delivered, the customer performed the acceptance testing to determine whether to accept the delivered software or to reject it.
- #9: Corrective Maintenance: This type of maintenance is carried out to correct errors that were not discovered during the product development phase. Perfective Maintenance: This type of maintenance is carried out to enhance the functionalities of the system based on the customer’s request. Adaptive Maintenance: Adaptive maintenance is usually required for porting the software to work in a new environment such as work on a new computer platform or with a new operating system.
- #10: Classical waterfall model is an idealistic model for software development. It is very simple, so it can be considered as the basis for other software development life cycle models.
- #11: No feedback path: In classical waterfall model evolution of a software from one phase to another phase is like a waterfall. It assumes that no error is ever committed by developers during any phases. Therefore, it does not incorporate any mechanism for error correction. Difficult to accommodate change requests: This model assumes that all the customer requirements can be completely and correctly defined at the beginning of the project, but actually customers’ requirements keep on changing with time. It is difficult to accommodate any change requests after the requirements specification phase is complete. No overlapping of phases: This model recommends that new phase can start only after the completion of the previous phase. But in real projects, this can’t be maintained. To increase the efficiency and reduce the cost, phases may overlap.
- #12: The Prototyping Model is one of the most popularly used Software Development Life Cycle Models (SDLC models).This model is used when the customers do not know the exact project requirements beforehand. In this model, a prototype of the end product is first developed, tested and refined as per customer feedback repeatedly till a final acceptable prototype is achieved which forms the basis for developing the final product.
- #14: Rapid Throwaway Prototyping – This technique offers a useful method of exploring ideas and getting customer feedback for each of them. In this method, a developed prototype need not necessarily be a part of the ultimately accepted prototype. Customer feedback helps in preventing unnecessary design faults and hence, the final prototype developed is of a better quality. Evolutionary Prototyping – In this method, the prototype developed initially is incrementally refined on the basis of customer feedback till it finally gets accepted. In comparison to Rapid Throwaway Prototyping, it offers a better approach which saves time as well as effort. This is because developing a prototype from scratch for every iteration of the process can sometimes be very frustrating for the developers.