Different software development life cycle methodologies undertake the development process in different ways. However, there is one common factor: their purpose. The system development methodologies aim to create high-quality software rapidly and efficiently. Professionals distinguish nine software development life cycle models:
- Waterfall Model
- Iterative Model
- Agile Model: Kanban & Scrum
- Incremental Model
- Spiral Model
- V-Model
- Lean Model
- RAD Model
- Software Prototype Model
To select the appropriate SDLC model, you have to consider the necessary level of expertise, budget, time, and other factors relevant to the process. However, it is advisable to understand the specifics of all software development models and methodologies in order to select the one that is the best option for your project. In the rest of this article, you’ll find a detailed description of each SDLC model as well as the specific aspects of their usage.
Waterfall Model
The Waterfall software development life cycle is the first and the simplest SDLC model. This methodology looks like a flow, as its stages are closely linked and follow one another sequentially. However, take into account that Waterfall represents quite a rigid approach to software development compared to other system development methods.
The stages of the Waterfall model system development life cycle are:
- analysis;
- design;
- development;
- testing;
- maintenance.
In the Waterfall model, the outcome of one phase becomes the input for the next sequential stage. Thus, it is crucial to complete each step before proceeding to the next one. You can undertake every SDLC phase only once in this model.
Pros
- a well-structured process with a strict sequence of activities;
- easy to prioritize tasks and set accurate deadlines;
- an opportunity to test each stage before its completion;
- every phase of the Waterfall model example has a concrete result and a defined review process.
Cons
- a lack of flexibility;
- high risks;
- inappropriate for projects with a long-term focus;
- Waterfall models in software engineering don’t provide the possibility to detect strengths and weaknesses of the project before its launch.
V-model
V-model is an extension of the Waterfall approach. This SDLC model incorporates testing, also known as “verification” steps, into every phase.
The V-Model comprises several validation stages, such as:
- Business Requirement Analysis;
- Architectural Design;
- System Design;
- Module Design;
- Coding Phase.
This SDLC model includes various testing options, which perform several functions:
- Unit testing carries out testing at code level, which helps to dispose of bugs at an early stage of the software development life cycle.
- Integration testing occurs at the stage of architecture design and performs verification of the internal modules.
- System testing verifies the software functionality and determines the level of its interaction with external modules.
- Acceptance testing improves the load and performance of the software and uncovers its compatibility with other systems.
Pros
- minimal risks;
- easy to understand and simple to manage;
- all the V-model stages follow one another in strict order.
Cons
- time-consuming development;
- no risk analysis actions;
- V-model is hard to modify once it is in the testing stage.
Incremental model
The Incremental model is linear, as all phases follow on from each other. In this model, SDLC consists of mini-projects, each of which leads to a full-fledged product. Once all these systems are put together into a final software system, the product is ready to be launched.
The Incremental model involves four phases:
- Requirement Analysis
- Design
- Coding
- Testing
Pros
- a gradual adjustment to new technologies;
- flexibility to changes in requirements;
- the Incremental model helps to predict risks related to the project’s budget.
Cons
- its phases are rigid and relatively difficult;
- problems can cause damage to the system architecture;
- the Incremental model requires an excellent project plan and design.
Spiral model
The Spiral model SDLC is a sequence of iterative and linear development stages, focusing on analysis. There are four phases of the Spiral development life cycle:
- Identification
- Risk Analysis
- Design
- Development & Testing
Spiral is the most flexible model out of all SDLC methodologies, as it combines the features of both the Waterfall and Prototyping approaches. This model emphasizes goal definition and risk evaluation, which are vital to the implementation stage. It is also based on client assessment and includes a linear approach to customer interaction.
Pros
- flexible designing and prototyping;
- accurate capturing of requirements;
- efficient risk management.
Cons
- a more complex management system;
- no specific deadlines;
- excessive amounts of documentation.
Agile model
The Agile model in SDLC combines iterative and incremental phases of software development. This methodology maximizes the system’s adaptability, which allows us to launch a product quickly and cost-effectively.
The Agile software development life cycle consists of a combination of the following stages:
- Planning
- Requirements Analysis
- Design
- Coding
- Unit Testing
- Acceptance Testing
The primary focus of Agile is a quick response to change and continuous development, so it will boost your product during the whole SDLC process.
Pros
- realistic approach with minimum risks and resource requirements;
- continuous communication and interaction with the customers;
- minimal rules for managing documentation.
Cons
- the Agile methodology life cycle requires the availability of an overall plan and rapid PM practice;
- it is dependent on interaction with users;
- lack of documentation and constant changing of requirements.
Kanban and Scrum are two powerful Agile methodologies that have the same principle but different practices. Let’s take a closer look at them.
Kanban
With Kanban, big tasks are divided into smaller pieces. Tasks are organized and moved on the board as they make their way through the traditional stages:
- To Do (Planned)
- In Progress
- In Review
- Completed (Done)
Pros
- very easy to implement — simple to understand and no need for structural changes or special setups;
- flexibility — tasks can be added, removed, or blocked according to the needs and priorities of the project at any time;
- promotes continuous improvement;
- promotes collaboration and teamwork.
Cons
- lack of timeframes;
- Kanban board requires constant attention as it may quickly become outdated and\or overcomplicated.
Scrum
Although with the Scrum approach you also divide big tasks into smaller ones, it is drastically different from Kanban. Scrum relies on prescribed roles (Product Owner, Scrum Master, Development Team) and sprints — work time frames of 2–4 weeks.
Pros
- clear workload and deadlines;
- continuous feedback from the customer ensures best results;
- constant communication helps to notice and resolve issues faster and easier.
Cons
- suitable only for experienced and committed teams;
- no predicted cost valuations and time limit for the entire project.
Lean model
The Lean SDLC model focuses on software efficiency and a quick delivery of the final result. This system development model includes aspects of the Agile model to reduce software waste and cost.
The first principle is the elimination of waste stage. Then comes the procedure of complete system optimization and the process of software structuring. The next statement — team empowerment that helps to avoid rash decision-making during product development.
Pros
- reduced costs;
- its streamlined approach allows for delivering more functionality within a shorter time period.
Cons
- the Lean SDLC is heavily dependent on team decisions;
- less scalable than other systems;
- requires strong documentation.
Iterative
The Iterative model of software development life cycle deals with improving the system for its efficient deployment. At first, you’ll have to identify the part of the software for implementation of additional requirements. At the final stage of this model, a new version of the software is obtained.
Pros
- the Iterative model is easy to use;
- ability to change the project’s scope and requirements at lower cost;
- easily identifies and eliminates risks.
Cons
- may require additional resources in the process of software development;
- needs more management attention;
- can’t analyze risks without highly skilled resources.
RAD Model (Rapid Application Development model)
The Rapid Application Development model is a program development methodology that doesn’t require specific planning. This SDLC model involves creating a prototype; i.e., a working model of the product with the same functionality as the actual project.
The projects implemented using the Rapid Application Development model in SDLC follow iterative and incremental phases. The RAD model stages are:
- Business & Data Modelling
- Process Modelling
- Testing
- Turnover
Pros
- progress through the SDLC can be measured;
- increases the reusability of software development components;
- reduces the time required for the SDLC life cycle.
Cons
- requires professional developers and designers;
- dependent on Modelling skills;
- more difficult management process.
Software Prototype Model
Developers prefer the Software Prototype Model as it helps to reveal client’s needs and requirements at an early stage of software launching. The software development phase allows incorporation of users’ opinions about the product, thus determining possible improvements for the project.
There are four stages of the Software Prototype Model:
- Requirements Identification
- Prototype Development
- Prototype Review
- Review and Enhance the Prototype
Pros
- allows increased user involvement in the project during its testing stage;
- reduces cost and time spent on SDLC;
- provides quick communication solutions for interaction with customers.
Cons
- Software Prototype Model can over-complicate the SDLC process;
- a greater number and diversity of prototypes and actual systems may confuse users.
As you can see, each SDLC model has its advantages and disadvantages. And it may seem challenging to choose the one that would work best for your project. To make the right choice that would lead your project to success, deepen your understanding of SDLC with our Ultimate Guide to Software Development Life Cycle Models.
