Software development lifecycle (SDLC) refers to a framework that identifies the different stages of software development. The SDLC meaning involves the comprehensive plan for building, deployment, and maintenance of the software.
SDLC covers the entire project development life cycle such as all the aspects involved in data collection of the requirements for product maintenance.
Types/models of SDLC
A software project development life cycle model represents the description when developing the software. Although the SDLC models may use different approaches, the general phases and activities are the same in all available models.
#1 Waterfall model
Waterfall model is the initial SDLC type that is being used in software development. It is also called as the linear sequential model. Using this model, the outcome of a particular phase is the basis for the succeeding phase. The development of the next phase only begins when the earlier phase is finalized.
- Initially, requirement gathering and analysis are conducted. After the requirement is satisfied, it is only when the system design is started. In the created SRS document, it shows the output for the requirement phase and functions as the system design input.
- In the system design software framework and design, the documents which are used as an input for the succeeding phase are developed and employed for implementation and coding.
- During the implementation phase, coding is held and the developed software is the input for the succeeding phase like testing.
- In the testing phase, the created code is evaluated carefully to identify software errors. The defects are logged into the tracking tool and are rechecked once resolved. Bug logging, retesting, and regression testing are examined once the software goes live.
- In the deployment phase, the developed code is shifted into production after the customer signs off the product.
- For any issues in the production environment, they are fixed by the developers under the maintenance phase.
Pros of the Waterfall model
This is a simple model that is easy to understand. It is one of the SDLC types that can be done in a systematic process. In every phase, the deliverables are well-defined. This eases the process and makes the project manageable.
Cons of Waterfall model
This model can be time-consuming and not applicable to short projects. In this SDLC type, you cannot begin a new phase until the current project is completed. This model cannot be employed for projects with uncertain requirements or project variables that keep on changing. It ensures that the requirement is very clear in the gathering and analysis phase and any modification in the later stages can increase the cost when changes would be necessary for all next phases.
#2 V-shaped model
V- model is also called the verification and validation model. In this model, this integrates development and testing. In both the V-model and waterfall model, they are quite similar. The only difference is that the test planning and its commencement are held at an early stage in V-model.
2.1 Verification phase
2.1.1 Requirement analysis. During this phase, all the necessary details are collected and evaluated. One particular activity in this phase is the review of the requirements.
2.1.2 System design. After allthe requirements are gathered, this is where the system design begins, including architecture, creation of product components, and documentation of the design blueprint.
2.1.3 High-level design. This details the modules’ framework or design of modules. This involves the functionality of the two modules.
2.1.4 Low-level design. This provides the architecture or design of the individual parts.
2.1.5 Coding. This is where the code development is conducted.
2.2 Validation phase
2.2.1 Unit testing. This is carried out through the unit cases that are created in the low-level design. The developer handles this task. This is done on the individual parts to check or identify initial defects.
2.2.2 Integration testing. This is conducted by employing integration test cases during the high-level design phase. This type of testing is performed on integrated modules. It is carried out by the testers.
2.2.3 System testing. This conducted in the system design phase, which examines the complete system’s functionality.
2.2.4 Acceptance testing. This is related to the requirement analysis phase and is conducted in the customer’s environment.
Pros of the V-model
This model is very simple and can be easily understood. The approach used in this model is suitable for mini projects where the requirement is defined and freezes in the initial stage. It follows a systematic approach that leads to a high-quality product.
Cons of the V-model
The V-shaped model is not recommended for existing projects. In case of modifications, the requirement at the later stage is very expensive.
#3 Prototype model
The is a prototype model that is created before the actual software. However, the prototype models have limited capabilities and inefficient functionalities as compared to the actual software. Using the dummy functions, they are useful for developing prototypes. This is a good mechanism for identifying the needs of the customers.
Software prototypes are created before developing the actual software to get essential customer feedback. Feedbacks from the customer are provided where the prototype has to be reviewed for any changes. This process persists until the customer signs of the prototype model.
At the first steps, the requirement gathering is conducted, then creating the initial design. Once the prototype is ready, it is sent to the customer for evaluation. With customer feedback, the requirement is refined modifying the prototype and again presented for customer approval. When the prototype is approved, this serves as a requirement for developing the actual software. The actual product is created through the waterfall model.
Pros of the prototype model
This model minimizes the development cost and time allotment upon the early detection of any defects. Identifying the missing requirement feature, functionality or related changes can be done in the evaluation phase and implemented when the prototyped is refined. By seeking the customer to be involved at the early stage, this avoids potential confusion in the details or misunderstanding of any functionality in the prototype.
Cons of the prototype model
Considering the customer is part of every phase, he can easily modify the end product’s requirement. In the process, there is a possibility of making the project scope more complex and extend the product’s delivery time.
#4 Spiral model
The model focuses on the iterative and prototype method. The model’s phases are held in the iterations. The model loops show the phase of the SDLC process, where the core loop involves the requirement gathering and analysis. This process undertakes several processes such as planning, risk analysis, development, and evaluation. The succeeding loop involves designing, implementation, and testing. Generally, the spiral model consists of four phases such as planning, risk analysis, engineering, and evaluation.
This phase consists of requirement gathering where all the necessary details are collected from the customer with proper documentation. As for the next phase, the software requirement specification document is developed.
4.2 Risk analysis
For this phase, the right solution is chosen for the involved risks. The analysis is held through prototype development.
For instance, the involved risk in data access from a remote database is that the rate of data access rate might be too slow. The risk can be solved by creating the data access subsystem prototype.
After conducting the risk analysis, the coding and testing follow.
The customer examines the created system and creates a plan for the succeeding iteration.
Pros of the spiral model
The prototype models play a vital part in extensively conducting the risk analysis. When the functionality needs to be modified, this is adopted in the next iteration.
Cons of the spiral model
This model can be best used specifically for huge projects. It may require high cost brought by several iterations, which can cause a longer time to achieve the final product.
#5 Iterative incremental model
This model classifies the product into mini components. For instance, the needed feature in the iteration is developed and implemented. In every iteration, it undergoes the phases such as requirement analysis, designing, coding, and testing. In conducting iterations, detailed planning is not needed.
After the iteration is finalized, product verification follows and sent to the customer for feedback. Once the evaluation is completed, the customer’s feedback is implemented in the succeeding iteration that includes the newly added feature. Hence, in the product enhancements and completed iterations, the final build contains all the product features.
The phases of iterative and incremental development model include inception, elaboration, construction, and transition.
5.1 Inception phase. This involves project requirement and scope.
5.2 Elaboration phase. In this phase, the working product architecture is submitted. This includes the identified risk found in the inception phase while achieving the non-functional requirements.
5.3 Construction phase. This is where the architecture has the codes for deployment and is developed through the functional requirement analysis, designing, implementation, and testing.
5.4 Transition phase. The deployment of the product is implemented in the production environment.
Pros of the iterative and incremental model
For any modification in the requirement, this can be easily implemented without additional cost. The necessary scope is integrated the succeeding iteration’s requirements. Also, this model involves risk analysis and identification of the iterations. During the initial stage, defects can be detected instantly. Considering the product is divided into mini parts, the product becomes manageable.
Cons of the iterative and incremental model
The product’s complete requirement and knowing what needs to be done enables it to be broken down and built incrementally.
#6 Big Bang model
This model no defined system. Both money and resources are combined as the input and output when developing a product which may or may not be the same with the customer requirements. The Big Bang model does not need too much planning and scheduling. The requirement analysis and coding are held by the developer, where he designs the product based on how he understands the instructions. This model is commonly used for small projects. No testing team or formal testing is conducted. This can lead to project failure most of the time.
Pros of the Big Bang model
This is considered a very simple model with less planning and scheduling. The developer enjoys flexibility when creating his own software.
Cons of the Big Bang model
This model is not applicable for large, existing and complex projects. It is described as high risk with an increased level of uncertainty.
#7 Agile model
This model is an integration of the Iterative and incremental model. This provides more flexibility when creating a product instead of the requirement. In Agile, a product is divided into mini incremental builds. It is not created as a complete product right away. Every provides increments in the features. The next build is developed on past performance.
Also, in agile, the iterations are called sprints. Every sprint may last for two to four weeks. When each sprint is completed, the product owner evaluates the product and approves it before delivering to the customer.
The customer feedback is critical in improving the created sprint. His suggestions are carried out in the next sprint. Testing is undertaken in every sprint to reduce potential risks or product failures.
Pros of the Agile model
This model enables more flexibility when adapting changes. It is where a new feature can be introduced easily. In every stage, customer satisfaction with his feedback and suggestions is highly regarded.
Cons of the Agile model
This model lacks proper documentation. It requires highly skilled resources. When the customer does not know what exactly product specifications he needs, then the project is deemed to fail.
Attaining the right SDLC is vital for successful project completion. In turn, this makes the project to be easily managed. Different SDLC models have pros and cons. The best model to use for any project can be identified using the various factors such as clarity of the specific requirements, system complexity, project size, cost, and skill limitation.