What Is Iterative and Incremental Development

by Anna Khrupa on Jul 11, 2022

Different types of projects have different management styles, organizational structures, and life cycles. There is no perfect one for each. Every project has its place, optimal balance, and development process, which can be either iterative, or with a high degree of change in the requirements and environment, or incremental, the one that delivers results on a regular basis. What does that mean?

Let’s have a look at what is iterative software development first.

What Is Iterative Software Development?

Iterative and incremental development are two different ways of managing a project, though they usually work hand in hand together. Let’s look at what does iterative means in software development. It refers to the repeated process, a series of steps of reviewing and testing the product until improved results are achieved.

The iterative model is a software development technique that breaks the construction of a product, which is expected to be changed and improved, into smaller parts. A company takes a general idea of what it is building without having a clear picture of it and layers everything else on top over time. In the iterative model, the requirements are broken down into multiple pieces or modules that are developed separately and integrated one after another. Each module is a standalone product, which can be presented to a client. The rest of the modules are added with every new release.

With an iterative approach, the team has something (that is going to be improved later) to offer to a user after each release. Unfinished work is modified in response to feedback, and the final product is evaluated during the whole development process. Everything starts with a vision that is fulfilled throughout the working process. The iterative model relies on a team that creates a program, learns from it as much as possible, and moves on to the next, better thing.

Let’s study in more detail what are the key benefits of iterative development and the downsides to it?

The Benefits of an Iterative Model

The iterative approach shows a number of benefits that might be useful for different software projects:

Rapid development of functionality;
Early user engagement;
Flexibility (the requirements and scope can be changed at any moment according to a customer request);
Simplicity in risk management;
Clarity (the result of the previous iteration is a starting point for the next one);
Suitability for large, complex, high-risk projects with unclear requirements;
Easiness in testing and debugging due to small iterations, which means fewer defects in a product;
Maximum business value in a minimum time frame;
High-quality feedback to a client;
More than one activity in one iteration;
Design efforts are spent only on what is planned to be done next;
The evolution of the application is visible to clients.

This technique does not work for small projects because a team is not confident in what the end product may look like. All the people in a team get a better understanding of what has to be delivered throughout the project. Thus, the time and effort required to reach the final goal are reduced. Before implementing the iterative approach, the requirements of the complete system have to be fully defined.

When to Use Iterative Model

Many things influence how the product is going to be delivered. If you have constantly updating requirements or the activities that are regularly repeated (checked and improved), and you are planning on frequent deliveries but not correcting a single one, that is when the iterative approach should be applied. In this model, a team focuses on gathering the requirements and feedback. It goes through a continuous cycle of planning, designing, implementing, testing, and evaluating. The iterative solution is applicable when the deadlines are tight or there is a need to get the application to the market early and the features may evolve with time without waiting for each of them to be completed before a release.

And now, let’s consider what is incremental software development and how can it be adopted in the work process?

What Is Incremental Software Development?

Incremental development is a software approach that is applied to develop smaller portions of software, one piece after another, building up functionalities gradually, with the product fully completed only at the end. The product is put in front of a user only after it has been constructed. According to this approach, a team knows and understands well what they are going for with their project. The software is branched into chunks or increments (among which the core increment is always what a team starts with) that are added one by one to complete the picture.

Compared to the iterative model, the incremental approach requires a higher number of resources as well as proper planning and designing. It provides deliverables that can be used by a user immediately. For example, there can be iterations every two or four weeks, providing something a user can use regularly.

So, what are the advantages of using incremental development and when do we use it?

The Benefits of an Incremental Model

The main advantages of adopting an incremental solution are:

Flexibility (suitable for companies with tight budgets as it is cheap to change the scope and requirements);
Rapid delivery (a working model is available early);
Reduced overall product failure risks (potential losses are easily identified and eliminated per module);
Parallel development (different teams can work on different parts of the same system simultaneously);
The ability to complete modules at different times.

The main downside of incremental development is the fact that a system has to be fully defined at the very beginning of the life cycle before it is broken down into several modules and constructed incrementally.

What indeed does incremental development mean in practice? When can a company adopt the approach to get the most use out of it?

When to Use Incremental Model

The incremental solution would be great if you deal with new technology, dynamic requirements, or expect small working deliveries with a high speed of getting the product to market. In other words, frequent releases as soon as possible. In this model, a team does not wait until everything in a project is completed but produces a single feature at a time.

But what is the difference between incremental and iterative model and how do they work together?

Using Both Iterative and Incremental Life Cycles

Iterative and incremental solutions are separate ideas, though they go together well. Both approaches take a team to the same result. The main difference is that with an incremental solution, you have to know every detail about a final product. In an iterative technique, a team works on everything at the same time and an improvement is made at any moment. Does that mean one approach is better than another? No. But it is crucial to realize when it is better to follow the incremental path and when it is better to be iterative. Doing both is the best of the options.

We are close to answering the question why is iterative and incremental development important for implementing a software project?

With no increments and iterations, there is a waterfall approach when all activities are performed once during the entire development process. A project in Agile represents both increments and iterations at the same time. The increment is an outcome of multiple iterations. A final product is delivered piece by piece. This method provides the ability to pause and adapt and minimizes risks, enhancing the product without putting in a whole ton of effort. In such a case, a team has a vision of a future product and a clear idea of what it is going to achieve. It takes the main features and presents them to a user as soon as possible. A product needs to be responsive to changes and should meet the requirements of a customer by receiving feedback frequently. And that is when the combination of both techniques works best.