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To produce high-quality software on time, development teams have to follow highly structured testing and processes to increase efficiency and reduce the chance for bugs to occur. These processes are called Software Development Life Cycles, and many such methodologies exist.
Here, we’ll focus on what SDLCs are, the stages that fall under it, and why they matter. We also look at specific SDLC methodologies in detail.
What is the Software Development Lifecycle?
The Software Development Life Cycle (SDLC) is a systematic, multistep, iterative process for building and delivering software applications. Development teams rely on a system development life cycle to create reliable software with as few issues as possible.
Phases of the Software Development Life Cycle
SDLC processes generally number at 6 distinct stages: planning, analysis, designing, development and testing, implementation, and maintenance. Each of them is briefly explained below.
The very first phase of the SDLC starts with requirement gathering. This is known as the planning stage. It is the most important phase of the entire SDLC from the perspective of project managers and stakeholders.
The planning stage answers such questions as:
- How will the software be used?
- What data will serve as the input of the software?
- What will be the output of the software?
- Who is going to use the software?
Once all the requirements are known, it’s time to analyze them for feasibility and validity. The team decides whether it will be possible to add the requirements to the software. After that, a Requirement Specification document is designed. This serves as the guide for carrying out the next phase of the SDLC.
This stage includes the designing of requirements specified in the very first phase of the SDLC. In addition to assisting in specifying hardware and system requirements, that stage also helps define the overall software architecture.
The system design specifications prepared in the designing phase serve as the input for the next i.e. fourth stage of the SDLC. During the designing phase, testers are required to form an apt testing strategy. It contains what needs to be tested, and how it needs to be tested.
4. Development & Testing
Some development teams consider development and testing to fall under a single-phase, others prefer to break it into two sub-phases. Irrespective of the choice a development team makes, the whole process remains the same. It’s all a matter of preference.
Once the system design documentation is complete, the whole task is divided into modules or units. After that, the actual coding begins.
Because this phase includes coding, it is the most important phase of the SDLC for the developer team. Moreover, this is the longest phase of the entire software development lifecycle. Once the code is fully developed, testing is carried out against the requirements.
Testing includes functional testing, such as acceptance testing, integration testing, system testing, and unit testing, as well as non-functional testing.
Also known as the deployment phase, the implementation phase occurs right after the successful testing of the software product. It is focused on delivering the software to the end-user or installing it onto the customer’s system(s).
The first thing that takes place once the product is delivered to the customer is beta testing. All bugs and enhancements are then reported to the developer team working on the project. Once the changes are complete, the final deployment takes place.
Finally, there’s the maintenance phase, which occurs over time after the product has been released. This phase deals with dealing with problems experienced by the customers/end-users while using the software.
Advantages and Disadvantages of SDLCs
Unsuitable when there are many iterations and/or regular reviews
Difficult to estimate costs and project overruns
Inflexible when it comes to changes in requirements
Effective development and design standards
Increased development cost and development time
Sets reliable evaluation costs and completion targets
Limited automation of documents and standards
Can monitor full-scale projects
The software is required to be thoroughly defined before the start
Precise user input
User input might be limited in certain scenarios
Tolerates changes to MIS in staffing
What is the best SDLC methodology?
There is no straight answer to this question, as the software life cycle model you choose will depend on the size and scope of the software you are building, on top of other factors. The best SDLC methodology will always come down to the requirements and project context.
There are also alternatives to the types of SDLC methodologies detailed further below. The most popular one is the RAD or Rapid Application Development. RAD offers implementation of CASE tools, joint application development, and prototyping. The advantages of RAD are active user involvement, a faster approach, and reduced development cost.
Is Waterfall a Methodology?
Yes, the waterfall is an SDLC methodology, and one of the oldest ones. The waterfall model is a linear methodology where every step must be completed before moving on to the next. All requirements and design choices are discussed first, and then deadlines are set for each stage’s completion.
Popular SDLC Methodologies
There are several types of Software Development Life Cycle models. Each one has its own set of advantages and disadvantages.
Though the approach might differ between models, each methodology has the goal of enabling the development team to deliver high-quality software in a cost-effective and quick manner. The following are 7 of the most popular SDLC methodologies.
1. Agile Software Development Life Cycle
Though the Agile model has existed for about two decades now, it has only gained traction within the past 5 - 10 years. The Agile methodology is so popular that some organizations are even using it for non-software-related projects.
Agile is based on an incremental and iterative approach. Fast failure is a notable aspect of it, and Agile features ongoing release cycles. Each of these features small changes over the previous release, with the product tested with each iteration.
A Scrum is a form of implementation of the Agile methodology that helps development teams structure complex project requirements. To complete assigned tasks, Scrum teams work in sprints, which is a period that lasts between 2 to 4 weeks.
Daily Scrum meetings are organized to help the complete team monitor progress made up until that point. The one in charge of the Scrum team is known as the ScrumMaster. As usual, it’s their responsibility to keep the team on track for meeting the goal.
- Capable of accommodating new changes or enhancements occurring during the development phase without a budget constraint
- Engages projects managers and business stakeholders and gets their feedback consistently throughout the software development process
- Fast development and testing allow for the recognition of existing gaps in the requirements or technologies being used. This makes easy to find alternative courses of action
- Helps development teams identify and address minor issues before becoming problematic
- Saves a great amount of cost and time thanks to the less documentation
- Almost impossible to determine the total effort required at the very beginning of development for full-size and complex projects
- High-risk when clients/end-users are unsure about requirements
- Requires valuable resources
- Puts less emphasis on designing and documentation processes
2. DevOps Software Development Life Cycle
The DevOps methodology emerged from two trends. First, the application of Agile and Lean models to the operations team. Second, the general shift in business to seeing the value of cooperation between the operations and development staff at all the stages of the SDLC process.
DevOps is a contraction for developers and operations. Following a DevOps methodology, the developer and operations teams work in tandem to accelerate and innovate the deployment and generation of highly-reliable software products.
Important highlights of the DevOps model are continuous feedback, discipline, process improvement, and automation of as many manual development processes as possible. Updates made to the software under development are brief but at a higher frequency.
- Cost and time need to be spent on unplanned work as well as bug fixing is reduced greatly
- Enhances the loyalty rates of the employees
- The entire development process takes less time as both operations and development teams learn about the potential obstructions simultaneously
- Faster failure recovery rates
- Higher credibility
- High risk of security issues, such as spoofing and man in the middle attacks, as the software development approach favors speeding up the software development process over security
3. Iterative Software Development Life Cycle
Instead of beginning with complete knowledge of requirements, project development teams following the iterative methodology implement a set of software requirements. Subsequently, they test, evaluate, and identify further requirements.
Each phase or iteration in this model produces a newer, better version of the software under development. A rinse and repeat approach is followed until the final software comes into shape.
A popular example of the Iterative model is the Rational Unified Process, a.k.a. RUP, developed by IBM’s Rational Software division.
- Allows developers and testers to identify functional or design flaws at the earliest possible. Hence, corrective measures can be made in a limited budget
- Capacity to plan parallel development
- Cost-effective to change the scope or requirements
- Each iteration is easy to manage
- Easily adapts to the changing needs of clients and the project
- Requires less time for documentation and offers more time for designing
- Suitable for agile organizations
- As not all requirements are gathered at the very beginning of the project, it is highly likely for system architecture or design issues to spring up
- Demands added management attention
- Each iteration is rigid
- Not suitable for smaller projects
- Requires a comparatively large number of resources
- Skill analysis requires highly skilled resources
4. Lean Software Development Life Cycle
The Lean methodology takes inspiration from lean manufacturing practices and principles. It follows a set of seven principles, which are:
- Eliminate waste
- Amplify/refine learning
- Decide as late as possible
- Deliver as fast as possible
- Empower the team
- Emphasize conceptual integrity
- See the whole/Operating from the top-level
Project teams working on the Lean model aim at finding opportunities to cut waste at every step of the SDLC process. Typically, this includes skipping unimportant meetings and reducing documentation.
In actuality, the Lean methodology is very much similar to the Agile methodology with some noteworthy differences.
The most important distinction between the two SDLC methodologies lies in terms of prioritizing customer satisfaction. The Agile model makes customer satisfaction a priority from the very beginning. Consequently, the project teams involved respond instantly to stakeholder feedback throughout the SDLC procedure.
On the other hand, Lean methodology gives the topmost priority to the elimination of waste. This is done in order to create more overall value for the clients.
- Applicable across team boundaries, doing well to integrate teams and optimize collaboration. Thus, it works well in line with the Agile and DevOps methodologies
- Facilitates delivering greater functionality in a shorter span of time
- Easily scalable, making it an apt fit as an alternative to contemporary SDLC methodologies designed for large, complex projects
- Empowers the project development team in terms of the decision-making process. As a result, it improves motivation
- Saves cost and time by eliminating unessential activities
- Demands excellent documentation, especially with respect to business requirements. Failing to do it might result in underdeveloped or wrongly developed areas pertaining to insufficient documentation
- Heavily team dependent. This means it is essential to put together an experienced team with a high skill level
- Relatively easy to lose focus
5. Spiral Software Development Life Cycle
The Spiral methodology is considered one of the most flexible SDLC models. Typically adopted for full-blown projects, the Spiral model lets development teams build a highly customized product.
Spiral methodology passes through four phases repeatedly until the project is completed. This allows for following multiple rounds of product refinement. These four phases are planning, risk analysis, engineering, and evaluation.
Each iteration of the Spiral methodology begins with predicting potential risks and the best way to avoid or mitigate them.
- Can accommodate new changes or functionality at later stages of development
- Cost estimation becomes as the prototype build is done in small increments
- Better risk management with repeated development
- Emphasizes customer feedback
- Faster development and systematic addition of features
- Demands risk management expertise
- High risk of not meeting budget or schedule deadlines
- Impractical for small projects
- Much more documentation due to intermediate phases
6. V Software Development Life Cycle
V Model stands for Verification and Validation Model. Though inspired by the Waterfall model, where the testing is done at the end of the project, it differs in that it introduces testing at every stage of development.
Similar to the Waterfall model, each next stage of the V model begins only when the previous one has been completed.
- Ability to avoid the downward flow of defects
- An apt fit for small projects with easily understandable requirements
- Higher chances of success
- Offers ease and simplicity
- Proactive tracking of potential defects
- Saves a lot of time as planning and designing related to testing is done before the actual coding takes place
- Even more rigid than the Waterfall model
- No early prototype creation is possible as the software is developed during the implementation phase
- Requirement and test documents need to be updated if changes are made during the development
7. Waterfall Software Development Life Cycle
Looking at this question asked on StackExchange, you will know that several experts believe that the Waterfall model was never meant to be a real, working SDLC methodology for developing software. Nonetheless, there are those taking the other side of the argument.
The waterfall model is one of the oldest surviving SDLC methodologies, and any discussion about SDLC methodologies is incomplete without it. Though mostly usurped by the Agile model, the Waterfall model follows a straightforward approach, which is a desirable quality for many software development teams.
Following the Waterfall methodology, a project development team needs to complete each phase step by step. There is no going backward with this model. Each successive phase of the SDLC process relies on the information gained from the preceding one.
- All potential development issues are researchable and manageable in the design phase
- Each stage of the model has a well-defined starting and ending point, making it easy to manage and monitor
- An easy and transparent testing process as the test scenarios are already detailed in the functional specification
- Needs and outcomes are clear
- Offers a greater degree of accuracy for cost estimation once the requirements are defined
- No “surprises” upon the completion
- Easy to understand as technical documentation is an essential aspect of the initial requirements gathering stage
- It takes much longer to make the final delivery, compared to iterative methodologies like the Agile model
- Doesn’t take into account changes due to the business plans or market influences during the planning process
- Lacks flexibility. The model cannot cater to new developments or changes made in the requirements after the original consultation
- Very difficult to conceptualize client needs in terms of functional specification during the requirements phase
That sums up our list of the 7 most popular SDLC methodologies. Choosing the right SDLC methodology for developing any kind of software is very important, and it’ll come down to business requirements and project context. A wrong choice can put the entire process several steps back or even make it an irrecoverable project.
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