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Software Development Life Cycle a.k.a. SDLC offers a systematic process for building as well as delivering software applications. It is a multistep, iterative process. Development teams rely on a system development life cycle to create efficacious software with as little issues as possible.
The generalized version of an SDLC has 6 distinct stages, namely: planning, analysis, designing, development & testing, implementation, and maintenance. Each of them is briefly explained in the following section.
Phases of the Software Development Life Cycle
Stage 1 – Planning
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 questions such as:
- How the software will be used?
- What data will serve as the input of the software?
- What data will be the output given by the software?
- Who is going to use the software?
Stage 2 – Analysis
Once all the requirements are collected, it’s time to analyze those requirements for feasibility and validity. Simply stating, it is studied whether it will be possible to add the requirements to the software or not.
Lastly, a Requirement Specification documented is made. It serves as the guide for carrying out the next phase of the SDLC. Once the requirement analysis is complete, the testing time following the Software Testing Life Cycle initiates the Test Planning phase.
Stage 3 – Designing
This stage includes the designing of requirements specified in the very first phase of the SDLC. In addition to assisting in specifying hardware as well as system requirements, Software Design also helps in defining the overall software architecture.
The system design specifications prepared in the designing phase serves as the input for the next i.e. fourth stage of the SDLC. During the designing phase, testers are required to come up with an apt testing strategy. It contains what needs to be tested, and how it needs to be tested.
Stage 4 – Development & Testing
While some development teams consider this phase as a single unit, others prefer to break it into two sub-phases. Irrespective of the choice a development team makes, the whole process remains the same. So, it’s all a matter of preference.
Once the system design documentation is complete, the whole task is divided into modules or units. Now, the actual coding starts.
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 of the same is carried against the requirements.
During this phase of the SDLC, various types of functional testing, such as acceptance testing, integration testing, system testing, and unit testing, as well as the non-functional testing is carried out.
Stage 5 – Implementation
Also known as the deployment phase, the implementation phase is carried out right after the successful testing of the software product. It is simply 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 the bugs and enhancements are then reported to the developer team working on the project afterward. Once all the changes are complete, the final deployment takes place.
Stage 6 – Maintenance
At last, the maintenance phase is executed. This phase deals with dealing with problems experienced by the customers/end-users that they experience while using the developed software. This needs to be done time and again.
Advantages and Issues with the SDLC
Disadvantages of using the SDLC emerge when there is a need for many iterations of the development or when stakeholders need to review the software being designed on a regular basis.
Pros of SDLC:
- Ample documentation
- Comprehensive steps
- Ease of maintenance
- Effective development and design standards
- Evaluation of cost as well as completion targets
- Possibility to monitor full-scale projects
- Powerful control
- Precise user input
- Tolerates changes in MIS of staffing
Cons of SDLC:
- Difficult to estimate costs and project overruns
- Inflexible to changes in requirements
- Increased development cost and development time
- Limited automation of document and standards
- Little parallelism
- The software is required to be thoroughly defined before beginning
- User input might be limited in some scenarios
There are several alternatives to SDLC. The most popular one is RAD or Rapid Application Development.
RAD offers implementation of CASE tools, joint application development, and prototyping. Desirable advantages of RAD are active user involvement, faster approach, and reduced development cost.
Popular SDLC Methodologies
There are several variants of the SDLC, known as models or methodologies, which are used by development teams around the world. Each one of them has their own set of advantages as well as disadvantages over the others.
Though the approach might differ from model to model, each SDLC methodology has the goal of enabling the development team to deliver high-quality software in a cost-effective and quick manner. Here are 7 of the most popular SDLC methodologies explained in detail:
Agile Software Development Life Cycle
Though the Agile model is available for almost a decade now, it has gained traction only recently. The popularity of the Agile methodology is so great that some organizations are even using it for non-software related projects.
Agile methodology is based on an incremental and iterative approach. Fast failure is a desirable aspect of the Agile methodology. It produces ongoing release cycles. Each of them features small changes over the previous release. The product being developed is tested at each iteration.
A Scrum is a form of implementation of the Agile methodology that helps development teams to structure complex project requirements. To complete assigned tasks, Scrum teams work in sprints, which is a period that could last anywhere between 2 to 4 weeks.
Daily Scrum meetings are organized to help the complete team monitor progress made throughout the project 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 the track for meeting the goal.
- Capable of accommodating new changes or enhancements occurring during the development phase without the budget constraint
- Engages projects managers and business stakeholders as well as get their feedback throughout the entire software development process
- Fast development and testing enable for recognizing existing gaps in the requirements or technologies being used. Hence, it is easy to find alternative pathways
- Helps development teams in identifying as well as addressing minor issues before they can evolve into bigger ones
- Saves a great amount of cost and time thanks to lesser documentation requirement
- Almost impossible to determine the effort estimation at the very beginning of the software development for full-size and complex projects
- High-risk probability when clients/end-users are unsure about requirements
- Necessitates experienced resources
- Puts less emphasis on designing and documentation processes
DevOps Software Development Life Cycle
The DevOps methodology emerged from two trends: the application of Agile and Lean models to the operations team and 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 as 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
- Entire development process takes less time as both operations and development teams get to know 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, neglects security in favor of speeding up the software development process
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 of the Iterative 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 ever-changing needs of the clients as well as the project
- Requires less time for documentation and gives 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 comparatively number of resources
- Skill analysis requires highly skilled resources
Lean Software Development Life Cycle
The Lean methodology takes inspiration from lean manufacturing practices and principles. The Lean model 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
- 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 complete 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.
Hence, 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 the waste. This is done in order to create more overall value for the clients.
- Applicable across team boundaries as well as the tendency to integrate teams and optimize collaboration. Thus, works well in line with the Agile and DevOps methodologies
- Capable to deliver more functionality in a shorter span of time
- Easily scalable makes it an apt fit as an alternative to contemporary SDLC methodologies designed for carrying out large, complex projects
- Empowers the project development team in terms of the decision-making process. Hence, improves the motivation for doing the job in the best way possible
- Saves cost and time by eliminating the unessential activity
- Demands excellent documentation, especially with respect to business requirements. Failing to 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
Spiral Software Development Life Cycle
The Spiral methodology is considered to be one of the most flexible SDLC models. Typically adopted for completing full-blown projects, Spiral model enables the project development teams to 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. The four phases followed by the Spiral methodology are planning, risk analysis, engineering, and evaluation.
Each iteration of the Spiral methodology begins with foreseeing potential risks as well as the best way to avoid or mitigate the same.
- Able to accommodate new changes or functionality at a later stage of the development
- As the prototype build is done in small increments, cost estimation becomes easy
- Better risk management with repeated development
- Emphasizes on 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
V Software Development Life Cycle
V Model stands for Verification and Validation Model. Though inspired from the Waterfall model, unlike it, where the testing is done at the end of the project, V Model introduces testing at each and every stage of the development.
Similar to the Waterfall model, each next stage of the V model begins only when the previous is completely done with.
- Ability to avoid the downward flow of defects
- An apt fit for small projects with easily understandable requirements
- Higher success chances
- Offers great ease and simplicity
- Proactive tracking of potential defects
- Saves a lot of time as planning and designing related to testing is done way before the actual coding takes place
- Even more rigid and less flexible 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 any changes had to be made amid the software development
Waterfall Software Development Life Cycle
If you follow 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, the debate also has those taking the side of the SDLC model.
Waterfall model is one of the oldest surviving SDLC methodologies. Hence, any discussion about SDLC methodologies is incomplete without it. Also, 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 one by one. Plus, there is no going back. 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 completely defined
- One gets one what has planned. Hence, no surprises upon the completion
- Very easy to understand as technical documentation is an essential aspect of the initial requirements gathering stage
- Compared to iterative methodologies like the Agile model, takes much longer to make the final delivery
- Doesn’t take into account changes due to the business plans or market influences during the planning process
- Lacks flexibility as it is very rigid. This means that the model is incapable to cater to new developments or changes made in the requirements occurring after the original consultation
- Very difficult to conceptualize client needs in terms of a functional specification during the requirements phase
That sums up the list of the 7 most popular SDLC methodologies. Choosing the right SDLC methodology for developing any kind of software is very important.
A wrong choice can put the entire process several steps back or even make it an irrecoverable project. Therefore, choose wisely.
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