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The Waterfall is a project management model co-opted into the software development life
cycle (SDLC). It takes a successional approach to software development by splitting
projects into independent phases and tackling them one after the other.
Each phase has its target set, and after its completion, the cycle proceeds. Phases cannot
overlap others in the Waterfall model, so progression relies on completing previous phases.
In addition to that, completed projects cannot be revisited. Major corrections mean the cycle has to be scrapped and restarted.
Waterfall is the oldest SDLC model and was the basis for developing all the other models.
However, its strict rules point to its history of being outside the software industry.
An example is that in building a house, you lay the foundation before building the walls. And
in the occurrence of a significant flaw in the foundation, it cannot be revisited unless the
project is collapsed and restarted.
In software development, however, there is leeway in revisiting the coding phase to address
minor bugs.
The waterfall model bases its operations on three core principles.
- Sequential Structure
- Robust Documentation
- Minimal customer involvement
Having already discussed the sequential nature of Waterfall, we will quickly look at the
other two.
Robust documentation means the waterfall model emphasises foreplanning and intensive
information gathering before the step is taken or code written.
The waterfall model also limits customer input during the development process, except via
controlled experiments during testing. This is because the model’s structure does not allow
for flexible iterations, meaning input cannot be easily implemented.
The Waterfall SDLC model typically flows down through 6 stages. It is visually represented
as a literal waterfall running down a slope. The water flows downward step-by-step and
cannot flow backwards onto a previous step.
Stages of Waterfall Model
Requirements
This stage aims to identify and gather all the information relevant to the SDLC. This
includes the full specifications of the customer's requirement, feasibility studies and other
documentation. These data can be gathered from interviews, questionnaires, and buzz
sessions. They analysed for flaws and limitations and then incorporated into a single
document called Software Requirements Specification (SRS).
Design
This phase aims to prepare the gathered document for coding. It is converted into a format
that the developers can easily represent with a programming language. Here also, suitable
programming languages and other architecture are agreed upon. The outcome of this
process is a document known as a Software Design Document(SDD).
The planning process in the design phase is usually split into two units called logical and
physical design.
- Logical design phase formulates and answers theoretical questions that may be encountered in the project. It discusses methods, solutions, principles, techniques and philosophies.
- Physical Design entails the inventory specification required to implement the discussed solution. It specifies hardware, software, personnel and architecture.
Coding
This is where hands-on production begins. By this stage, the developers clearly understand
what the end product should be. The focus is to bring life to the ideas constructed in the
SDD through written code. In large-scale or complex projects, the developers may be split
into smaller teams to work on different units of the project. These units are tested
independently before they are integrated into the overall SDLC.
Testing
The conclusion of the coding phase means that a product has been built. That product will
then be rigorously tested to determine its functionality and identify flaws or 'bugs' that
impede customer requirements or satisfaction. On an enormous scope, this process is
called Software testing. It is split into functional and non-functional testing.
Functional: Unit testing, Integration testing, System testing and acceptance testing.
Non-functional: Security, performance, usability, and compatibility testing.
Suppose the product passes all of these tests, the SDLC flows on. If it does not, the
detection of minor flaws will result in a forced repeat of the coding phase. This is the only
point in the Waterfall model where a revisit is allowed. However, if the flaws in coding are
major, the entire SDLC will be restarted.
Sometimes customers can get involved using a User Acceptance Test agreement at this
stage. This is done to get feedback from the intended user of the product. It aims to
uncover bugs that have gone unnoticed by the developers because they only surface
during day-day use. It is the last phase of testing before deployment.
Deployment
use by the intended customer.
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Maintenance
This is arguably the most essential part of the SDLC. It is an indefinite process that exists to
keep the customer satisfied. It involves corrections, code adaptations & general customer
service as required. Maintenance continues until perfection is achieved.
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Advantages of Waterfall Model
- It is easy to understand, manage and use
- It enforces structured, disciplined organisation
- Detailed documentation and clearly defined steps make it easy to replicate
- Accurate projection of estimated cost and timeline
- Robust documentation helps point out errors early
- It clearly defines milestones and progress due to the structural and planned
approach
- Limited customer input can prevent an overload of suggestions and changes
that could derail the project's fundamental ideals.
- Detailed, structured and documented procedures make it easy to replicate.
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Disadvantages of Waterfall Model
- A chain reaction of delays. Because the phases are not permitted to overlap,
a delay in one step stalls other phases too.
- Upfront cost estimation and strict adherence to the schema mean
unforeseen customer demands and their costs might not be accounted for
- It may take longer than other, more flexible models
- It is not flexible, usually restarting the entire project to correct a flaw
- It is not ideal for complex and high-risk projects
- It does not handle changes, scope adjustments and updates well.
- No working product is available until the later stages of the project lifecycle.
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When to use Waterfall Model
As with all other SDLC methodologies, The Waterfall model produces the best results when
applied in suitable environments or circumstances. Usage of the Waterfall model is less and
less these days, as other models have built on its advantages to counter its disadvantages.
However, the methodology remains relevant and useful if applied in the right environment.
Some factors that determine if you need this SDLC framework for your projects are:
- A project with precise requirements
- A short project which can be easily restarted from scratch
- A project that involves stable and well-understood technology
- The risk factor is minimum
- Resources are readily available
- A project that is unlikely to require too many changes
- A product that does not demand extensive customer feedback
Alternatives to Waterfall
With the usage of the Waterfall model dwindling in modern times, other methodologies are
taking centre stage. Prominent among them are:
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Agile Methodology
Agile is the software development approach that is defined by breaking down projects into
small, flexible and incremental units, as opposed to a single massive launch. It aims to
provide value through receipt and integration of exhaustive customer input, made easy by
its flexibility, adaptability and continuously iterative nature. Agile development cycles are
ever-evolving and constantly improving.
Spiral Model
The Spiral model is a risk-driven framework that emphasises risk analysis and
management. It combines the iterative features of other models with the structured linear
approach of the waterfall model, only applying resources to areas with the lowest possibility
of failure. The visual representation of the Spiral model is a literal spiral, with each loop
representing a phase of the SDLC.
DevOps
DevOps is a combination of development and IT operations teams to increase efficiency,
cross-team communication, productivity and high-speed delivery in the SDLC. Its main goal
is to provide high-quality software in a shortened systems development life cycle through
Software and Tools for Waterfall Model
Gantt Chart
A Gantt chart is a detailed horizontal bar chart that shows information about project
management activities, resources, planning, and dependencies, as well as their timelines
and deadlines.
These charts depict sequential phases of an SDLC, enabling easy projection of
dependencies and subtasks to each phase of the process. They provide a clear view of
activities for each phase and their start and finish dates. It is an ideal and essential tool for
the Waterfall SDLC methodology.
Most Waterfall model software tools offer a platform for Gantt. Some of them are:
Wrike
Wrike is a customisable tool that helps teams configure workflows, dashboards, and other
features according to requirements. It supports an interactive Gantt chart and allows users
to create and share timeline views, task dependencies, snapshots, baseline, and critical
path analysis.
Monday.com
Monday.com is an online project management platform that helps teams to centralise
information. It has an interactive Gantt chart that makes the Waterfall model easy to track
and execute. It easily keeps track of milestones and important dates. It also features
automation, real-time updates, project dashboards, and templates.
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Smartsheet
Smartsheet is a cloud-based project management platform with flexibility for use cases and
departments. It offers a rich set of views, workflows, reports, and dashboards to capture
and track your plans, resources, and schedules.
MindManager
MindManager is a mapping tool that minimises the number of tools you need by offering the
capabilities you need within one resource. It supports setting up the Gantt chart and easily
storing, sharing, and retrieving files within the chart, adding the relevant customer requirements to the tasks and steps that need them.
Merlin Project
With Merlin Project, you can create the flow of your tasks, determine duration and
dependencies, and define fixed milestones. This tool automatically transfers your input to
the work breakdown view. It also helps you transform a complex plan into an elegant and
expressive mind map.
Conclusion
The waterfall model, though less popular, remains relevant in software development and
project management today due to its structured and well-organised framework. When
applied to the right projects, the Waterfall model still delivers satisfactory results.
Wazobia Technologies
Content Writer
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