Waterfall or agile implementation - which model to choose?

Waterfall or agile implementation - which model to choose?

There is no single, universal method for implementing IT systems that works in the realities of each project and enterprise. Now two forms dominate: the so-called waterfall and the flexible model. The Waterfall model is the traditional project management model. This is a linear and sequential approach. Tasks completed in one stage should be reviewed and verified before moving on to the next stage. Agile methodology, in turn, is a phased approach based on a flexible response to change.

What are the advantages and disadvantages of these methods? What projects do they work best for?

Waterfall Model

Waterfall project management is a sequential approach that breaks a project into separate phases. Typical steps include requirements gathering, analysis, design, coding, internal testing, acceptance testing, installation, implementation, training, and commissioning. The next step can only be continued if the previous step was completed successfully.

One of the biggest problems associated with the waterfall model is the fact that the recipient of the system can only check the result of the work after the completion of a single stage or the entire project. In a negative scenario, this may lead to a situation where the client at the stage of acceptance tests claims that the effect does not meet his expectations. This is a waste of time and money, and greatly increases the risk of project cancellation.
Large design documentation is associated with the waterfall model. It often uses guidelines and best practices found in the PRINCE2 methodology or PMI (Project Management Institute) guidelines, but the high level of formality limits the flexibility of the project and reduces the ability to respond to large numbers or significant changes in requirements.

All this makes the waterfall model not recommended for long-term, high-risk and uncertain projects. This method will not work if the full requirements and deliverables cannot be determined during the planning phase. If significant changes need to be made to the project scope, it may become unavoidable to cancel the project and start over.

Benefits of the waterfall model:

• Easy planning and design thanks to the precise assumption made at the beginning of the project;
• system design covers the entire scope of work from the very beginning;
• precise definition of the scope of work;
• Relatively simple budget definition;
• easy check of the work progress.

Disadvantages of the waterfall model:

• a rigid structure makes it difficult to make changes;
• uncertainty factor is not taken into account;
• Confirmation of fulfillment of project requirements occurs upon its completion;
  requires a lot of documentation;
• transition to the next phase is possible only after the end of the previous one;
• limited customer acquisition can lead to lower satisfaction with results;
• The cascading approach is risky for long-term projects whose end result is removed in time.

Flexible Model

Agile methodologies allow you to implement an IT system using small steps. This ensures high process flexibility, better control and high adaptability of solutions to changing needs. The idea behind a flexible implementation is to get started quickly with a standard version of a program, and then gradually iteratively tweak it to meet the specific needs of the user.

The Agile method emphasizes close collaboration and customer satisfaction. Defines time-limited milestones, called sprints or time boxes, typically lasting one week, two weeks, or a month.

At the beginning of each sprint, a list of tasks is created according to the defined priorities together with the client. The customer can freely change the priority for all not yet developed system functions. At the end of the sprint, the system provider and customer review and evaluate progress.

A flexible model simplifies cost rationalization. When software vendors offer to implement a system in the traditional model, they usually take on a buffer to protect themselves from unexpected situations. Due to the need to forecast labor costs in the long term, such a proposal is often overpriced.

Benefits of a flexible model

• Fast commissioning by starting work on a basic version that allows you to spread over time the often most time-consuming project steps of adjusting specific user requirements;
• efficient testing by splitting it into small chunks and updating it constantly;
• accelerated software lifecycle;
• quick check of assumptions, the client can quickly seeh, how the different functions of the system work in practice;
• constant involvement of the customer in the process of creating subsequent iterations of the system helps to avoid misunderstandings, and therefore loss of time and resources;
• more customer involvement in system development often results in better user experience;
  rationalization of costs.

• requires significant client involvement;
• Project team members should be knowledgeable about the principles that govern the Agile methodology and should be highly motivated;
• Total project costs are more difficult to estimate than for the waterfall model;
• less documentation than the waterfall model.

Waterfall and agile are the sum of the differences

The Idea - Agile is an incremental and iterative approach, waterfall is a linear and sequential approach.

Construction - Agile divides the project into sprints, and the waterfall method into phases.

Application - agile method helps in the implementation of many small projects, the waterfall model is better suited to complete one large project.

Customer Relationship - Agile focuses on close collaboration with the client, waterfall model focuses on the implementation of project assumptions.

Evaluation – in the agile approach, projects are monitored on an ongoing basis during daily meetings, evaluation in the waterfall model occurs at the end of this phase.

Introduced Changes - agile allows you to change the requirements at any time, the waterfall approach stays within the intended scope.

Testing - in the Agile model, testing is carried out on an ongoing basis, in the waterfall model, it is carried out at the final phase of the project.

The waterfall model and the agile model are fundamentally different approaches to project management. Both methods have significant advantages and disadvantages. Which of them will be the best in a given situation depends mainly on the attitude of the customer, the financing model, the scale and time horizon of implementation.