What is SDLC (Software Development Life Cycle)?

What is SDLC?

Definition of Software Development Life Cycle

SDLC stands for Software Development Life Cycle. It consists of many clearly defined and distinct work phases. System engineers and developers use them to plan for, design, build, test, and deliver information systems.

Software Development Process – Overview

It aims at producing high-quality systems that meet or exceed customer expectations based on their requirements. Software Development Life Cycle does so by delivering systems that move through each clearly defined phase within a scheduled time frame and cost estimate.

It greatly influences creating a well-managed, comprehensive structure of a development project in the IT world. Thus, taking care of all the essential technical methods required to meet the ultimate fruition.

Software Development Life Cycle is slightly complicated but very substantial. It follows certain compelling models and contains different phases, from the product’s ideation to complete fulfillment. Whether it’s quality, accuracy, or precision, the software development life cycle acts as a methodical, systematic process for building software or a mobile application.

It is regarded as an industry benchmark and ensures better work quality by emphasizing smooth flow and correctness of the end product. Hence, the results are high-quality software as per customer expectations. Also, its detailed planning and road map helps you to plan and build software of your vision.

Importance of SDLC

A question may arise in your mind as to why is the Software Development Life Cycle important. Now, there are countless advantages of SDLC to have for your design project. Though here are the common ones:

  • It helps you to clarify what the problem or goal is. You can easily go ahead while taking on a large project. Software Development Life Cycle lets you see the goals and issues to implement your plans with precision and relevance.
  • You can design the project with clarity. The project cannot jump from one stage to another until it completes the prior stage, and the project manager signs it off. You can create a formal review at the end of each phase to give you maximum management control.
  • It properly tests it before installation. If you execute your project using an Software Development Life Cycle, then it goes through some necessary checks and balances. You can rest-assure about its precision testing before entering the installation stage.
  • Even if a key project member leaves, the new member can pick up from where it left. Normally, in case of missing or incomplete paperwork, the new member has to start from the beginning or even change the project to make proper sense. But, the well-designed software development life cycle lets the new project member continue the process without any complications. 
  • A project manager can powerfully manage a project provided the deliverables are completed on time and within the budget. It is very easy to stick to a budget when you have a well-organized plan that lets you see all the timetables and costs. The project can submit their work to an integrated system that flags anything due. It saves the project manager’s time on micro-managing. Hence, he or she can spend more time improving the production and efficiency of the project.
  • The project can continuously loop around until perfect. The stages feed them back into the earlier stages. Hence, the Software Development Life Cycle model provides flexibility to the project.
  • When it comes to designing and implementing a project, Software Development Life Cycle is the solution. It’s the best way to ensure optimal control, minimize problems, and allow project managers to run production. That, too, without worrying about micromanaging the project members. 

So, it sums up the benefits of Software Development Life Cycle for your design project.

SDLC Phases

What are the SDLC stages/phases? – How does the SDLC work?

Every software development company goes through various stages for systematic software development. Here is a brief overview of all the Systems Development Life Cycle phases required for creating flawless software from planning to design and development.

Planning

Planning is the root of the Software Development Life Cycle phases. In this phase, project leaders evaluate the terms of the project. It includes calculating material and labor costs, creating timetables with target goals, projects’ team, and leadership structure.

Planning also includes feedback from stakeholders. You can even take feedback from potential customers, developers, subject matter experts, and sales reps. 

Planning clearly defines the scope and purpose of the application. It plots the course and provisions the team for effectively creating the software. The planning process also sets boundaries and makes sure the project does not expand or shift from its original purpose.

Read further about Planning → Planning Stage in SDLC

Define Requirements

It’s a part of the planning, and it determines what the application is supposed to do and its requirements. In this phase, you clearly define and document the product requirements. Later, getting them approved from the customer or the market analysis.

You can do it through an SRS (Software Requirement Specification) document that consists of all the product requirements you need to design and develop during the project life cycle. For example, a social media application requires the ability to connect with a friend. However, an inventory program may require a search feature. 

It also includes defining the resources required to build the project. Let’s say a team might develop software to control a custom manufacturing machine. Then, you can say that the machine is a requirement in this Software Development process.

Read further details → Define Requirements in SDLC

Design

SRS is a reference for product architects to come up with the best architecture for the product to be developed. As per the SRS requirements, you can propose and document more than one design approach for the product architecture in a DDS – Design Document Specification.

All the important stakeholders review the DDS. Based on parameters like risk assessment, product robustness, design modularity, budget, and time constraints, selecting the best design approach is done.

The design approach speaks of all the product’s architectural modules and its communication and data flow representation with external and third-party modules. You must clearly define all the proposed architecture modules’ internal design, taking care of DDS’s minor details.

Prototyping is also a part of the Design phase. It is like one of the early versions of software in the iterative software development model. The process demonstrates a basic idea of how the application would look and work. You can show such a “hands-on” design to stakeholders and use their feedback to improve the application. Making changes during the prototype phase is less expensive than rewriting the code for the development phase.

Read more → Designing in SDLC

Development

It is the actual writing of the program. A single developer might be writing a small project, but you can break it up for a large project, and several teams can work on it. You can use Access Control or Source Code Management application in this phase. Such systems help developers to track changes to the code. It also ensures compatibility between different team projects and achieving the target goals.

The coding process consists of many other tasks too. It is critical to find and fix errors and glitches. So, developers need to brush their skills if required and work as one team. Often, tasks such as waiting for test results or code compilation hold up the development process to run an application. Software Development Life Cycle plays a crucial role in such cases. It anticipates such delays so that developers can perform other important duties.

Software developers appreciate relevant instructions and explanations. Documentation could be a formal process, like wiring a user for the application. However, it can be informal, too, like comments in the source code explaining why a developer used a particular procedure. Companies striving to create software that’s easy and intuitive also benefit from the documentation.

Documentation can also be a quick guided tour of the app’s basic features that you display on the first launch. It may be video tutorials for complex tasks. Written documentation such as user guides, troubleshooting guides, and FAQs help users solve problems or technical issues.

Read further → Development Phase in SDLC

Testing

Testing is a crucial part of software development life cycle phases as it’s important to test an application before you make it available to the users. Like security testing, you can automate much of the testing. However, you can do another testing only in a specific environment. So, you can consider creating a simulated production environment for complex deployments.

Testing must ensure that everything functions smoothly. You can test different parts of the application to confirm if they are working seamlessly together. Also, performance test, to reduce any lags or hangs in processing. The testing phase helps in reducing the number of bugs and glitches that users encounter. Thus, leading to higher user satisfaction and better usage rate.

Read further → Testing Phase in SDLC

Deployment

Here, the application is made available to the users. Many companies opt for automating the deployment phase. It can be as simple as a download link and payment portal on the company website. You can also download the application on a smartphone.

Deployment can also be complex at times. Upgrading a company-wide database to a newly-developed app is one such example. As the database uses several other systems too, integrating the upgrade can take more time and effort.

Read more → Deployment Phase in SDLC

Maintenance

By this point, the Software Development Life Cycle is almost finished. The users start using the application too. However, the maintenance phase is still very important. Here, the users discover bugs that were unfound during the testing phase. So, you need to resolve them as soon as possible.

Apart from bug fixes, you may need to upgrade, maintain, polish, redesign, and enhance the application as per the customer feedback. It is a crucial time to modify the application’s functionalities to increase its performance vigorously. Hence, you would meet the actual needs of your target audience.

Read more about Maintenance → Maintenance Phase in SDLC

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Software Development Life Cycle Models

A good software engineer should have excellent knowledge of choosing the SDLC model based on the project context and business requirements. You can think of SDLC Methodologies as tools that would help you in better delivery of software projects.

There are various types of Software Development Methodologies. Hence, it becomes important to know and understand about each Model and when to use it. Their advantages and disadvantages will give you a better idea of which one is more suitable for your project.

So, let’s have a look at each of the Software Development Life Cycle Models for a better understanding.

Waterfall Model

The SDLC Waterfall model is the oldest of all the methodologies. You can also refer to it as a linear-sequential life cycle model. The Waterfall Model is very simple to use and understand. Here, each phase completes before the next phase begins, and there is no overlapping in the stages. It is the earliest of all the software development life cycle models.

The Model illustrates the software development process in a linear sequential flow. It means that any phase in the development process would begin only if the previous phase is complete. The phases do not overlap here.

Waterfall Model – Design

It was the first widely used Software Development Life Cycle Model in Software Engineering to ensure the success of the project. Here, the whole process of software development divides into separate phases. One phase’ input acts as the output for the next phase sequentially.

The following illustration represents the different phases of the Waterfall Model System Development Life Cycle:

Below are the sequential phases in the SDLC Waterfall Model:

  • Requirement Gathering and Analysis: All the system’s possible requirements you want to develop are captured here and documented in a requirement specification document.
  • System Design: System Design: A study of the requirement specifications from the first phase and the system design is developed. This design helps in specifying the hardware and system requirements and defines the overall system architecture.
  • Implementation: The system then develops in small programs called units that get integrated into the next phase. All the units are developed and tested for their functionality, referred to as Unit Testing.
  • Testing and Integration: The units you develop in the implementation phase are integrated into a system after testing all the units. After the integration, the entire system is tested for any faults and failures.
  • System Deployment: Once you do the functional and non-functional testing, the product is deployed in the customer environment or released into the market.
  • Maintenance: Some issues may come up in the client environment. Patches help in fixing those issues. The better versions would enhance the product. Thus, maintenance helps to deliver these changes in the customer environment.

All these Software Development Life Cycle phases cascade to each other, and you can see the progress flowing steadily downwards (like a waterfall) through the phases. The next phase starts after achieving some defined set of goals for the previous phase and is signed off. Hence, the name “Waterfall Model.” The phases do not overlap here.

Waterfall Model – Application

Every software you develop is different and demands a proper software development life cycle approach based on internal and external factors. The use of the Waterfall Software Development Model is the most appropriate in the following situations:

  • Well documented, clear, and has fixed requirements.
  • Stable product definition.
  • Technology is not dynamic and is easily understood.
  • No ambiguous requirements.
  • Ample resources with the required expertise are available for the product.
  • The project is short.

Advantages of Waterfall Model

Waterfall development allows for departmentalization and control. You can set a schedule with deadlines for each stage of development. Plus, a product proceeding through the development process model phases one by one.

Development moves across concept, design, implementation, testing, installation, and troubleshooting. It then ends up at operation and maintenance. Each development phase proceeds in strict order. 

Below are some of the major benefits of Waterfall Model:

  • Easy and simple to understand and use.
  • The rigidity of the ModelModel makes it easier to manage. Each of the phases has specific deliverables and review processes.
  • Phases are processed and completed, one each at a time.
  • Works very well for smaller projects where the requirements are well understood.
  • Clear and well-defined stages.
  • Easy to arrange tasks.
  • Well understood, milestones.
  • Well documented process and results.

Disadvantages of Waterfall Model

It does not enable much reflection or revision. Once an application comes into the testing phase, it is very difficult to go back and change the one that was not well-documented or thought of in the concept stage.

Here are some of the major cons of the Waterfall Model SDLC:

  • It does not produce working software until late during the life cycle.
  • High risk and uncertainty.
  • It is not a good model for object-oriented, complex projects.
  • Not suitable for projects where requirements are at a moderate to high risk of changing. So, it has a higher risk and uncertainty level.
  • It is a poor model for long, ongoing projects.
  • It is difficult to measure progress within the stages.
  • Cannot accommodate changing environments.
  • Integration happens as a “big-bang” at the very end. So, it does not allow identifying any technological or business bottleneck earlier.
  • A project can end on adjusting the scope during the life cycle.
  • sting the scope during the life cycle.

Further Reading → Waterfall Model Complete Guide 

Iterative Model

The Iterative SDLC Methodology begins with a simple implementation of a small set of software requirements. It iteratively enhances the evolving versions until you implement the entire system and deploy it. 

The Model does not attempt to start with a full specification of requirements. The development starts by specifying and implementing just a part of the software you can review to identify further requirements. The process then repeats, producing a new version of the software at the end of each Model’s iteration.

Iterative Model – Design

The Iterative process begins with a simple implementation of a subset of software requirements. That iteratively enhances the evolving versions until you implement the whole system. The design modifications are made at each iteration, adding new functional capabilities. The key factor behind this method is to develop a system through repeated cycles (Iterative) and in smaller portions at a time (Incremental).

The following illustrates the representation of the Iterative and Incremental Model:

Iterative and Incremental development is a mixture of both – Iterative and incremental build models for development. While developing the software, more than one iteration of the software development cycle may simultaneously progress. You may describe such a process as an “Evolutionary Acquisition” or “Incremental Build” Approach.

In the Incremental Model, the fundamental requirement gets divided into various builds. The development module passes through the requirements, design, implementation, and testing phases during each iteration. Each subsequent release adds function to the previous releases. Then, the process would continue till the entire system is ready as per the requirements.

The key to the successful use of an iterative software development lifecycle is rigorous validation of requirements. Plus, verification and testing of each version of the software against the requirements within each cycle of the Model. As the software passes through successive cycles, you must repeat the tests and extend them to verify each software version. 

Iterative Model – Application

Just like other SDLC Methodologies, Iterative and Incremental development has some specific applications in the software industry. You can often use it in the following scenarios:

  • The requirements of the entire system are clearly defined and understood.
  • You must specify the major requirements. However, some requested enhancements or functionalities may evolve with time.
  • There is time for market constraint.
  • The development team is using and learning a new technology while working on the project.
  • Resources with required skill sets are unavailable and to be used on a contract basis for particular iterations.
  • It involves some high-risk features and goals that may alter in the future. 

Advantages of Iterative Model

The benefit of using this Model is that there is a working model of the system at a very early development stage. That makes it easier to find functional or design flaws. Finding issues in the earlier stages of development enables you to take corrective measures with a minimum budget.

The advantages of the Iterative and Incremental Model are as follows:

  • You can develop some working functionalities quickly and early in the life cycle.
  • You can obtain the results earlier and periodically.
  • You can plan for parallel development.
  • You can measure progress.
  • It is less costly to change the scope/requirements.
  • Testing and debugging is easy during smaller iterations.
  • You can easily identify and resolve risks during iteration. Plus, each iteration is an easily managed milestone.
  • It is easy to work as the high-risk part happens earlier.
  • It delivers operational products with every increment.
  • You can apply issues, challenges, and risks identified from each increment to the next increment.
  • Risk analysis is better.
  • It supports changing requirements.
  • Initial operation time is less.
  • It is better suited for large and mission-critical projects.
  • It produces the software early during the life cycle, which facilitates customer evaluation and feedback.

Disadvantages of Iterative Model

It applies only to large and bulky software development projects. That is because it is hard to break a small software system into further small serviceable increments.

Below are the disadvantages of the Iterative Model SDLC and Incremental Model:

  • You may require more resources.
  • Despite the lesser change in cost, it is not suitable for changing requirements.
  • It needs more managerial attention.
  • You may face system architecture or design issues as all the requirements do not gather at the beginning of the entire life cycle.
  • You may require a definition of the complete system to define increments.
  • It is not suitable for smaller projects.
  • It has more management complexity.
  • The end of the project may be unknown; hence it is a risk.
  • You will require highly skilled resources for risk analysis.
  • Projects’ progress highly depends on the risk analysis phase. 

Further Reading → Managing Iterative Development Projects Guide

Spiral Model SDLC

The Spiral SDLC Methodology combines iterative development with the systematic, controlled aspects of the Waterfall Model. It’s the combination of the Iterative development process model and sequential linear development model. 

That is the Waterfall model with a high emphasis on risk analysis. It allows the incremental release/refinement of the product through each iteration around the spiral. 

Spiral Model – Design

The Spiral Model consists of four phases. A software project would repeatedly pass through these phases in iterations called Spirals.

Identification

It begins with gathering the business requirements in the baseline spiral. As the product matures, identification of system, sub-system, and unit requirements are all made in this phase in the subsequent spirals. 

It also includes the understanding of system requirements by continuous communication between the customer and the system analyst. At the end of the spiral, it is time to deploy the product in the identified market.

Design

It starts with the conceptual design in the baseline spiral and includes architectural, logical, physical, and final designs in the subsequent spirals.

Construct or Build

It refers to the production of actual software products at every spiral. In a baseline spiral, when you think of a product and develop the design, the developed POC (Proof of Concept) helps you with customer feedback. 

With more clarity on requirements and design details in the subsequent trials, a working model of the software known as “build” is produced with a version number. Such builds are sent to the customer for feedback.

Evaluation and Risk Analysis

It includes identifying, estimating, and monitoring technical feasibility and management risks like schedule slippage and cost over-run. After testing the build, the customer evaluates the software and provides feedback at the end of the first iteration.

The following illustrates the representation of the Spiral Model SDLC, listing the activities in each phase:

Based on customer evaluation, the software development process enters the next iteration. It then subsequently follows the linear approach to implement customer-suggested feedback. The process of iterations along the spirals goes on throughout the life of the software.

Spiral Model – Application

It’s widely used in the software industry as it is in sync with any product’s natural development process. That is, learning with the maturity that involves minimal risk for the customer and development firms.

The below pointers show the typical uses of a Spiral Model:

  • When you have a budget constraint, and risk evaluation is important.
  • Medium to high-risk projects.
  • You have a long-term project commitment due to potential changes to economic priorities.
  • When the customers are unsure of their requirements, and it is usually the case.
  • When the requirements are complex, and you need an evaluation to get clarity.
  • You need to release a new product line in phases to get customer feedback.
  • You expect significant changes in the product during the development cycle.

Advantages of Spiral Model

It allows the product elements that you need to add in when they become available or known. It assures of no conflict with previous requirements and design.

It’s consistent with approaches with multiple software builds and releases that enable an orderly transition to maintenance activity. Plus, the Spiral Model forces an early user involvement in the system development effort. 

The benefits of using Spiral SDLC Methodology are as follows:

  • You can accommodate the changing requirements. 
  • It allows extensive use of prototypes.
  • It lets you capture the requirements more accurately.
  • Users can see the system early.
  • You can divide the development into smaller parts and develop them earlier for better risk management. 

Disadvantages of Spiral Model

It takes strict management to complete such products and involves the risk of running the spiral in an indefinite loop. Hence, the discipline of change and the extent of taking change requests is very crucial to develop and deploy the product successfully. 

Below are the cons of using Spiral Model SDLC:

  • Its management is more complex.
  • You may not know the end of the project earlier.
  • It is not suitable for small or low-risk projects and costly for small projects.
  • Its process is complex.
  • The spiral may go on indefinitely.
  • Its large number of intermediate stages may require excessive documentation.

SDLC V-Model

It’s an SDLC Model where the execution of processes happens sequentially in a V-shape. You can also call it the “Verification and Validation Model.”

The V-Model in SDLC is an extension of the Waterfall Model. It works on the association of a testing phase for each corresponding development phase. Thus, there is a directly associated testing phase for every single phase in the development cycle. It’s a highly disciplined model, and the next phase would start only after the completion of the previous one. 

V-Shaped SDLC Model – Design

Here, you can plan the corresponding testing phase of the development process parallelly. On one side of the ‘V,’ there are Verification phases and Validation phases on the other side. The coding phase would join the two sides of the V-Model.

The following illustration would depict the different phases of the V-Shaped Model in SDLC:

SDLC V-Model – Verification Phases

There are many verification phases in the SDLC V-Model. Its detailed explanation is as follows:

Business Requirement Analysis

It’s the first phase in the development to understand the product requirements from the customer’s perspective. The process involves thorough communication with the customer to understand his expectations and requirements. 

It’s a crucial activity and needs more attention as most customers are unsure about their needs. Then, you can do the acceptance test design planning. Thus, using the business requirements as an input for acceptance testing.

System Design

Once you have a clear and detailed idea about the product requirements, it is time to design the whole system. The system has a better understanding and detailing of the complete hardware and its communication setup under development. You can then develop the system test plan based on the system design. Doing it at an earlier stage leaves more time for the actual test execution later on.

Architectural Design

You understand and design the architectural specifications in this phase. More than one technical approach is proposed here, and you can make the final decision based on the technical and financial feasibility. Then, the system design is further broken down into modules, taking up different functionalities. You can also refer to it as High-Level Design (HLD).

The transfer of data and communication between the internal modules and other systems is clearly understood and defined in this phase. With such information, you can design and document integration tests at this stage.

Module Design

Here, all the system modules’ detailed internal design is specified, referred to as Low-Level Design (LLD). The designs must be compatible with other modules in the system architecture and external systems. The unit tests are a vital part of any development process and help to eliminate the maximum errors and faults at an early stage. You can design them in this stage based on the internal module designs.

SDLC V-Model – Coding Phase

The actual coding of the system modules you design in the design phase is taken up. You decide on the best suitable programming language based on the system and architectural requirements.

The coding is done based on the coding guidelines and standards. The code goes through various code reviews, and you can optimize it for the best performance before checking the final build into the repository. 

SDLC V-Model – Validation Phases

Here is a brief description of different validation phases in a V-Model:

Unit Testing

The unit tests that you design in the module design phase are executed during this phase. It’s the testing at the code level and helps eliminate bugs early, though you cannot uncover all the defects. 

Integration Testing

It is associated with the architectural design phase. You perform integration tests to test the coexistence and communication of the internal modules within the system.

System Testing

It is directly associated with the system design phase. The system tests check the complete system functionality and communication under development with the externals systems. Most of the issues related to software and hardware do not cover during this system test execution.

Acceptance Testing

It is linked with the business requirement analysis phase and includes testing the product in a user environment. Acceptance tests uncover the compatibility issues with other systems available in the user environment. It also lets you discover non-functional problems such as performance and load defects in the actual user environment. 

SDLC V-Model – Application

It is almost the same as the Waterfall Model as they both are sequential. Your requirements must be clear before the project starts as it’s expensive going back and making the changes. The Model is used in the medical development field as it is strictly a disciplined domain. 

The following pointers represent the scenarios where you can use the V-Model application:

  • You have well-defined, clearly documented, and fixed requirements.
  • The product definition is stable.
  • When you don’t have a dynamic technology and your team easily understands it.
  • There are no undefined or ambiguous requirements.
  • You have a short project.

Advantages of V-Model

It is easy to understand and apply. The simplicity of this Model makes it easier to manage. Now, let’s have a look at the benefits of the V-Model in brief.

  • It’s a high discipline model, and phases get completed one at a time.
  • It works good for smaller projects where requirements are well understood.
  • It’s easy and simple to understand and use.
  • You can easily manage it due to its rigidity. Each phase has specific deliverables and the review process.

Disadvantages of V-Model

The V-Model is not flexible to changes. So, in case of a common requirement change in today’s dynamic world, it’s very costly to make such changes.

The cons of V-Shaped SDLC Model are as follows:

  • It has a high risk and is uncertain.
  • It is not a good model for complex and object-oriented projects.
  • It’s a poor model for long and ongoing projects.
  • It is not suitable for projects where the requirements are at a moderate to high risk of changing.
  • Once your application is in the testing stage, it is difficult to go back and change its functionality.
  • You can’t produce any working software until late during the life cycle. 

Big Bang Model SDLC

It is an SDLC Model where you do not follow any specific process. The development starts with the required money and efforts as the input and the developed software as the output. Though, it may or may not be as per customer requirements. 

The SDLC Big Bang Model does not follow a specific process and needs very little planning. Even the customers are unsure about their wants, and the requirements get implemented on the fly without much analysis. You can follow this Model for small projects where the development teams are small.

Big Bang Model SDLC – Design and Application

The Model comprises focusing all the possible resources in the software development and coding, with little to no planning. It understands and implements the requirements as they come. There may or may not need to revamp the entire software in case of changes.

The Big Bang Model is ideal for small projects with one or more developers working together and is useful for academic or practice projects. It is a perfect model when you do not understand the requirements well and do not have the final release date.

Advantages of Big Bang Model

It is simple and requires little to no planning. The Model is easy to manage and does not require any formal procedure. 

The advantages of Big Bang Model are as under:

  • It’s a very simple model.
  • It needs little to no planning.
  • It is easy to manage.
  • It requires minimum resources.
  • It provides flexibility to developers.
  • It is a good learning aid for students or newcomers.

Disadvantages of Big Bang Model

It is a high-risk model, and changes in the requirements or misunderstood requirements may lead to complete reversal or scraping of the project. The Big Bang Model is ideal for small or repetitive projects with minimum risks.

The disadvantages of Big Bang Model are as under:

  • It has a high risk and is uncertain.
  • It is not a good model for complex and object-oriented projects.
  • It is a poor model for long and ongoing projects.
  • It can be very expensive if you misunderstand the requirements.

Agile Model

Agile Software Development Methodology is a combination of iterative and incremental process models. The Model focuses on process adaptability and customer satisfaction by rapid delivery of working software products. 

It breaks the product into small incremental builds, provided in iterations. Each iteration generally lasts from one to three weeks. It involves cross-functional teams working simultaneously on various areas as below:

  • Planning 
  • Requirement Analysis
  • Designing 
  • Coding 
  • Unit Testing
  • Acceptance Testing

At the end of the iteration, you can display a working product to the customer and important stakeholders.

What is Agile Methodology?

The Agile SDLC Methodology believes that you need to handle every project differently and tailor the existing methods to best suit the project requirements. Here, the tasks are divided into time boxes (small time frames) to deliver specific release features. 

It takes on the Iterative approach and delivers the working software build after each iteration. Each build is incremental, and the final build holds all the features as per the customer requirements.

Below is a graphical representation of the Agile Model:

The Agile Software Development Methodology started quite earlier and became popular with time due to its flexibility and adaptability.

The popular Agile methods include Rational Unified Process (1994), Scrum (1995), Extreme Programming (1996), Crystal Clear, Feature Driven Development, Adaptive Software Development, and Dynamic Systems Development Method (DSDM) (1995). They are collectively referred to as Agile Methodologies after the publishing of Agile Manifesto in 2001.

Below are the Agile Manifesto Principles:

  • Individuals and interactions – Self-organization and motivation are important in Agile development, as are interactions like co-location and pair programming.
  • Working software – Instead of depending on the documentation, demo operating software works as the best communication mode to understand the customer requirements. 
  • Customer collaboration – As you cannot completely gather the requirements at the beginning of the project, continuous customer interaction is vital to get proper product requirements.
  • Responding to change – Agile development aims to focus on quick responses to change and continuous development.

Agile vs Traditional SDLC Models

Agile Model SDLC works on adaptive software development methods, while the traditional SDLC models like the Waterfall Model works on a predictive approach. The predictive teams in the traditional SDLC models work with detailed planning. They have a complete forecast of the same tasks and features you need to deliver in the next few months or the product life cycle.

The predictive methods completely depend on the requirement analysis and planning done at the beginning of the cycle. Any changes that you want to incorporate goes through strict change control management and prioritization.

Agile uses an adaptive approach that needs no detailed planning, and there is clarity on future tasks only concerning the features you want to develop. There is a feature-driven development, and the team adapts to the changing product requirements dynamically. The product is often tested through the release iterations, minimizing the risk of any major failures in the future. 

Customer Interaction is the backbone of Agile SDLC Methodology, and open communication with minimum documentation is its typical feature. The Agile teams collaborate and are most often located in the same geographical location. 

Pros and Cons of Agile Model

The Agile SDLC Methodologies are very popular in the software world recently. However, it may not always be suitable for all the products. So, let’s discuss some of the pros and cons of the Agile Model.

The advantages of Agile Model are as below:

  • It’s a very realistic approach to software development.
  • It promotes teamwork and cross-training.
  • You can rapidly develop its functionality and demonstrate it.
  • Its resource requirements are minimum.
  • It is suitable for fixed or changing requirements.
  • It delivers early and partial working solutions.
  • It is a good model for steadily changing environments.
  • It has minimum rules and easily employed documentation.
  • It enables concurrent development and delivery within the overall planned context.
  • It requires little to no planning.
  • It is very easy to manage.
  • It provides flexibility to developers.

Now, the disadvantages of Agile Model are as under:

  • The Model is not suitable for handling complex dependencies.
  • There is more risk of sustainability, extensibility, and maintainability.
  • An overall plan, Agile PM, and an Agile leader practice is crucial as it will not work without them.
  • The strict delivery management would dictate the scope, functionality to be delivered, and the adjustments to meet the deadlines.
  • The Agile Model heavily depends on customer interaction. So, if the customer is unclear, then the team will drive in the wrong direction.
  • Since there is minimum documentation generated, there is a very high individual dependency.
  • The technology transfer to new team members can be challenging due to a lack of documentation.

Rapid Application Development

The RAD (Rapid Application Development) Model works on prototyping and iterative development with no specific planning. The process of writing the software itself includes the planning necessary to develop the product.

The Rapid Application Development focuses on the following pointers: 

  • Gathering customer requirements through workshops or focus groups.
  • Early testing of prototypes by the customer using iterative concepts.
  • Reuse of the existing prototypes.
  • Continuous integration, and
  • Rapid delivery.

What is RAD?

Rapid Application Development is a software development method that makes use of minimal planning, favoring rapid prototyping. A prototype is a working model, functionally equivalent to a component of the product.

In the RAD SDLC Model, you develop the functional modules parallel as prototypes and integrate them to form the complete product for faster product delivery. As there is no detailed preplanning, it’s easier to incorporate the changes within the development process.

The RAD projects follow iterative and incremental models and have small teams. They comprise developers, domain experts, customer representatives, and other IT resources working progressively on their components or prototypes.

The most important aspect to make this Model successful is to ensure that the developed prototypes are reusable.

RAD Model – Design

It distributes the analysis, design, builds, and test phases into a series of short, iterative development cycles.

Now, the various phases of the Rapid Application Development Model are as below:

Business Modelling

You can design the business model for the product under development as per the flow and distribution of information between various business channels. Complete business analysis helps you find vital information for the business. You would know how you can obtain it, how and when the information process, and the factors influencing the successful flow of information. 

Data Modelling

The information you gather in the Business Modelling phase is reviewed and analyzed to form sets of data objects vital for the business. The attributes of all the data sets are identified and defined. The relation between such data objects is established and defined in detail under the business model.

Process Modelling

The data object sets that you define in the Data Modelling stage are converted to establish the business information flow required to achieve specific business objectives as per the business model. The process model for any changes to the data object sets is defined in this phase. Process descriptions to add, delete, retrieve, or modify a data object are given.

Application Generation

Here, you can build the actual system and do coding using automation tools to convert the process and data models into actual prototypes.

Testing and Turnover

The overall testing time gets reduced in the RAD Model as you can independently test the prototypes during each iteration. However, you need to thoroughly test the data flow and the interfaces between all the components with complete test coverage. As you have already tested most of the programming components, it reduces the risk of any major issues.

The following example describes the RAD SDLC Methodology in detail:

RAD Model vs Traditional SDLC

The traditional SDLC follows a rigid process with a high emphasis on requirement analysis and gathering before the coding would start. Before the project starts, it puts pressure on the customer to sign off the requirements, and the customer gets no feel of the product due to the unavailability of working build for a long time.

The customer would want to make some changes after he gets to see the software. However, the change process is very rigid and may not be feasible to incorporate major product changes in the traditional SDLC.

The RAD Model focuses on incremental and iterative delivery of working models to the customer. It results in rapid delivery to the customer and their involvement during the complete product development cycle. Thus, reducing the risk of non-conformance with the actual user requirements.

RAD Model – Application

You can successfully RAD Model to the projects in which clear modularization is possible. If you are unable to break the project into modules, then the RAD may fail.

Now, the following pointers will help you with where you can use the Rapid Application Development Methodology:

  • You can use RAD only when you can modularize a system to deliver incrementally.
  • You can use it when there is a high availability of designers for Modelling.
  • You should use it only if the budget permits the use of automated code generating tools.
  •  You must choose the RAD SDLC Model only if the domain experts are available with relevant business knowledge.
  • You should use it where the requirements change during the project, and you have to present the working prototypes to customers in small iterations of 2-3 months.

Rapid Application Development Pros and Cons

The RAD Model provides you rapid delivery as it reduces the overall development time due to the reusability of components and parallel development. RAD works well equipped that high-skilled engineers are available, and the customer is equally committed to achieving the targeted prototype in the given time frame. If there is a lack of commitment on any of the sides, then the Model may fail. 

The advantages of RAD Model are as follows:

  • You can accommodate the changing requirements.
  • You can measure progress.
  • You can shorten the iteration time using powerful RAD tools.
  • It provides productivity with minimal people in a short period.
  • Reduced development time.
  • It increases the reusability of components.
  • It offers quick initial reviews.
  • It encourages customer feedback.
  • Integration, right from the beginning, solves the problems related to integration. 

The disadvantages of RAD Model are as under:

  • It highly depends on technically strong team members to identify the business requirements.
  • You can build only the system that you can modularize using RAD.
  • It requires highly skilled developers.
  • It is highly dependent on modeling skills.
  • It is inapplicable to cheaper projects as the cost of Modelling, and automated code generation is very high.
  • The management complexity is more.
  • It is more suitable for systems that are component-based and scalable.
  • It requires user involvement throughout the life cycle.
  • It is more suitable for projects that require shorter development times.

Prototyping Model

The Prototyping Model in Software Engineering refers to building software application prototypes that display the product’s functionality under development. But, it may not hold the exact logic of the original software.

Prototyping is gaining more popularity as a software development model as it lets you understand customer requirements at an early stage of development.

It helps you get valuable feedback from the customer. Plus, the Model also helps software designers and developers understand what is expected from the product under development.

What is Prototyping?

A prototype is a working software model with some limited functionality. It does not always hold the exact logic used in the actual software application. So, a prototype is an extra effort that you can consider under effort estimation.

The Prototype Model of SDLC is mainly used to enable users to evaluate developer proposals and try them out before implementation. It also helps you understand user-specific requirements, and the developers may not have considered them during the product design.

Below mentioned is a stepwise approach as to how to design a software prototype:

Basic Requirement Identification

It includes the understanding of very basic product requirements, especially in terms of the user interface. You can ignore the more intricate details of the internal design and external aspects like security and performance at this stage.

Initial Prototype Development

In this stage, you develop an initial prototype to showcase the basic requirements and provide user interfaces. However, these features may not work in the same manner internally in the developed software. You can make use of workarounds to give the same look and feel to the customer in the developed prototype.

Prototype Review

It’s time to present the developed prototype to the customer and other important stakeholders in the project. The feedback is then collected in an organized manner and used for further enhancements in the product under development. 

Revise and Enhance the Prototype

You can discuss the feedback and the review comments at this stage. You can negotiate with the customer based on the factors like – time and budget constraints and the technical feasibility of the actual implementation. The accepted changes are again incorporated in the new, developed prototype, and this cycle keeps repeating until the customer expectations meet.

Prototypes can have two dimensions – horizontal or vertical. The horizontal one displays the user interface for the product and offers a broader view of the entire system without concentrating on the internal functions. On the other hand, a vertical prototype elaborates a specific function or a sub-system in the product.     

The purpose of both the prototypes, horizontal, and vertical, is different. The horizontal prototypes are used to get more information on the business requirements and the user interface level. You can also present it in the sales demos to get business in the market. However, the vertical prototypes are technical and are used to get details for the sub-system’s exact functioning—for example, database requirements, data processing loads, and interaction in a given sub-system.

Prototyping Model – Types

There are various types of Prototypes used in the industry. The major Prototyping types widely used are as follows:

Rapid/Throwaway Prototyping

It is also known as Rapid or Close-ended prototyping. It uses very little effort with minimum requirement analysis to build a prototype. Once you understand the actual requirements, you can discard the prototype, and you can develop the actual system with a clearer understanding of user requirements.

Evolutionary Prototyping

Evolutionary prototyping is known as breadboard prototyping. It works on building the actual functional prototypes with minimal functionality in the beginning. The developed prototype forms the heart of the future prototypes above which the entire system is built. Making use of evolutionary prototyping, you can include the well-understood requirements in the prototype. Thus, adding the requirements as and when they are understood.

Incremental Prototyping

It refers to building multiple functional prototypes of various sub-systems and integrating all the available prototypes to form a complete system.

Extreme Prototyping

You can mainly use Extreme prototyping in the web development domain, and it consists of three sequential phases. First, you can present a basic prototype of all the existing pages in the HTML format. 

Then, you can simulate the data processing using a prototype services layer. Thus, implementing and integrating the services to the final one. This process is known as Extreme Prototyping. It is useful to draw your attention to the second phase of the process, where a functional UI is built with very little regard to the actual services. 

Prototyping Methodology – Application

Prototyping is useful to you in developing systems with high levels of user interactions, such as online systems. Systems that require users to fill out forms or go through various screens before processing the data can use prototyping very effectively. It helps you to give an exact look and feel even before you develop the actual software. 

Advantages of Prototyping Model

The Prototyping Model is useful in typical cases, and you must make the decision very carefully so that your efforts put considerable value to the developed product. 

The benefits of using Prototyping Model are as follows:

  • It helps you in increasing the user involvement in the product even before the implementation.
  • The display of the system’s working model helps users get a better understanding of the system under development.
  • It reduces your time and cost as you can detect the defects much earlier.
  • Its quicker user feedback leads to better solutions.
  • You can easily identify the missing functionality.
  • It helps you to identify confusing or difficult functions.

Disadvantages of Prototyping Model

The cons of using the Prototyping Model are as follows:

  • It involves the risk of insufficient requirement analysis. Thus, leading to too much dependency on the prototype.
  • It may confuse the users in the prototypes and actual systems.
  • It may increase the system’s complexity as the scope of the system may expand beyond original plans.
  • The developers may try to reuse the existing prototypes to build the actual system, even when it is technically unfeasible.
  • If you do not monitor it properly, you may have to put in a lot of effort to build prototypes.

Planning to Hire Software Developers for your project? We have a team of highly experienced and dedicated developers in the business. 

SDLC FAQs

  • Why is Software Development Life Cycle (SDLC) used?

It is essential to have an SDLC in place, to transform the idea of a project into a functional and completely operational structure. Apart from covering the technical aspects of system development, SDLC helps with process development, user experience, change management, and policies.

  • Which SDLC Model is better – Agile or Waterfall?

Agile Model is suitable for all kinds of projects. There are very few companies that follow the Waterfall Model. It’s suitable only if the application is small, simple, and there are no changes in the requirement. Hence, Agile is preferable. 

  • Does Google use Agile or Waterfall?

Google adopted a combination of Agile Scrum and Waterfall Methodologies as it let them use procedures they were comfortable with. They can switch between methods based on the needs of each project.

  • Why is the SDLC Waterfall Model less preferable?

The disadvantage of Waterfall Software Development is that it disallows much reflection or revision. Once your application is in the testing stage, it is difficult to go back and change something that was not well-documented or thought upon in the concept stage. 

  • Why is Agile Model SDLC the best?

The Agile model in a Systems Development Life Cycle (SDLC) allows companies to develop and release software changes in small segments frequently. It will enable management to implement changes more quickly and the project team to be more flexible to scope changes.

  • Is Scrum an SDLC?

Scrum is not an SDLC as it does not cover all of the generally accepted things that are part of an SDLC. There are no mentions of common initiation or inception activities such as forming a team or identifying an initial scope or how the work will be funded. 

  • What is the difference between SDLC and Scrum?

In both SDLC & Scrum methods, an iteration or module is not passed on until done. But the difference between the two is that in Scrum projects, evaluation of a module is present before it is passed along. In traditional SDLC, the project flow passes along without stopping with hopes of a good outcome.

  • What is STLC?

STLC stands for Software Testing Life Cycle. It is a sequence of different activities carried out by the testing team to ensure the quality of the software or the product. As soon as the development phase is over, the testers are ready with test cases and start to execute. 

  • Which testing is performed first?

In a comprehensive software development environment, you usually do the bottom-up testing first, followed by top-down testing. The whole process concludes with multiple tests of the complete application, preferably in scenarios designed to mimic actual situations. 

  • What is SDLC Policy?

The purpose of the Systems Development Life Cycle (SDLC) Policy is to describe the requirements for developing and/or implementing new software and systems at the University of Kansas. Also, ensuring that all development work is compliant related to any or all regulatory, statutory, federal, and/or state guidelines.

  • Why do we need secure SDLC?

The main benefits of adopting a secure SDLC include: 

  1. It makes security an ongoing concern – including all stakeholders in the security considerations.
  2. It helps to detect flaws early in the development process – reducing business risks for the organization.
  3. It reduces costs by detecting and resolving issues early in the life cycle.
  • What is the most significant process lapse in secure SDLC?

The most significant lapse in secure SDLC is the provision of Finance. It requires a considerable amount of finance to secure SDLC, and any disruption in it will lead to failure.

  • What is the source code in SDLC?

Source code consists of statements created with a visual programming tool or a text editor and then saved in a file. It is the most permanent form of a program, even though it may later be modified, improved, or upgraded. It can be either static or dynamic. 

  • What is Assassin in SDLC?

Assassin is an Idle Process Management (IPM) software product that automatically performs pre-defined actions on processes that are idle, inactive, or meet particular conditions.

  • How many companies use Agile?

The report shows 97% of organizations are now practicing Agile Methodologies. You can’t say that its use is universal. However, only 22% of respondents report that all their teams are Agile, 26% more than half, and 48% less than half.

Dev Upadhyay
WRITTEN BY Dev Upadhyay

Dev Upadhyay is a content writer at Openxcell - one of India's top ten mobile app development companies. He loves to write, read, and binge-watch documentaries about science and society. Being a travel-freak, he's very adventurous and fun-loving.

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