Incremental Model

by StarAgile

April 06, 2020
Category Agile and Scrum


When you want to complete a huge task it is a good practice to divide them into small jobs. By doing so it is easy to handle one work at a time. Also, it is possible to figure out the mistakes and correct them in the initial stage rather than allowing it to spread across the project. 

Imagine the construction of a 4 story building in which every floor will go through all phases independently and finally come to shape.

But, there are a few questions you must answer to understand this concept. How will you know the right way to split the task? Whether you randomly divide them or is there a pattern to do so? We will answer your questions in the coming section and provide you an idea about how to do it successfully. 

We are talking about the incremental model. Yes, this is the method that gained popularity in agile methodology. In other words, the secret of agile framework success is because of the incremental delivery process it follows. 

What is it? 

Understand the term incremental model with the example given below.

All you want is to multiply two numbers. How do we do this? In steps and that is depicted in the image. Every step you append a new process. There are five steps in this in total. So you know how to divide them into modules. 

Likewise, in software development based on the requirement, you need to divide them into increments. Take each module through all phases and get them ready for release. Each increment ready for release will get added to the next increment in parallel to another increment that underwent all phases. As we know agile is an iterative process this becomes easy to implement. 

What are the chief characteristics of this model? 

Mini project 

The entire development work will be divided into modules. Which means each module is a project. It will be independent and all the phases of software development must be completed for this one module. 

Building a partial system 

The entire team will work towards building the system performing their task to complete every module. Each of these systems will be cumulatively added and that becomes a final system when it reaches the end and gets the end product as required by the customer. 

Prioritization 

However, the product owner will decide on the backlog prioritization as each module is independent of the other. The most important task will get completed first and will be approved by the customer to build the remaining increments. 

Freezing 

Every requirement of the increments gets frozen after it is duly developed. 

Incremental model and its phases 

From the above image, you can quickly understand that the chief 4 phases include 

  1. Analyzing the requirement 
  2. Designing
  3. Coding
  4. Testing  

1.  The software specification is collected and analyzed for the need for development and the number of increments required. Also, what must be present in each increment is identified. The priority of the increments is accessed. 

2. Then high-end designing takes place for that particular module based on the specifications and the analyzed requirement. 

3. Next comes coding. The required coding is executed by the developers that will help to give a shape to the product. 

4.  Finally, testing is done for ascertaining the system after the system gets deployed. It allows making corrections in case the testing team suggest any. Based on that the work gets back to coding or design team. 

It is considered complete when all the different stakeholders complete the task and get approval from the others too. This step gets repeated for every increment and that cumulatively adds to the next increment. 

When to use this? 

It must become a habit to use the incremental model in the following situation. Initially, you might find it difficult to know when to use it. Therefore experts have suggested the following thumb rules to know when to use. 

  • After understanding the requirement clearly. When you know that it requires a lot of work and dividing them into modules will help. Also, the size of the requirement will give you an idea about how many increments are needed.
  • If the customer demands an early release, then you have to divide work into modules and get them done concurrently.
  • Based on the risk and the goal of the project. The high-risk and extended goal will require implementing the incremental model.
  • Every product development company must think about this model as it helps to achieve the goal quickly and cost-effectively. 

What do you benefit from this model?

  • The process of generation becomes quick as the work is divided into modules.
  • The time required to complete the task can be reduced due to the division of work.
  • The incremental model is flexible and cost-effective. Changing the scope and requirement can be done at any time during development. 
  • Access to the work at any stage becomes possible and the customer can include other requirements too. They can also identify errors and offer suggestions 

Drawbacks

  • Every phase is rigid and overlapping becomes tough 
  • Failing to understand the requirement at the beginning will demolish the entire purpose of incrementing. 
  • Detailed planning is required and hence time-consuming
  • Every increment gets cumulatively added and hence problem rectification in one unit might impact on the other.

However, by exercising caution and gaining experience one can easily do away with the negatives of the incremental model and use it for effective software development. 

Types of incremental model 

There are two different types, namely, the staged delivery and parallel developmental. The former is used to construct only a single part of the work at a given time. Whereas the latter as the name suggests each module is completed concurrently and then added to the final system. 

Iterative vs Incremental model

We call agile an iterative process and incremental too, then are they both the same and different. Both are used in agile projects under different scenarios. You can understand how they work from the table given below. 

Iterative
Incremental
The development process is cyclic 
The development process happens in steps and every step will contain all phases.
Iteration and improvement happens concurrently
Improvement is suggested at the end of each increment
Creation of simple prototype with limited features and added to the development 
Moving through the development phase starting from requirement analysis to testing. 
Your action and our suggestion 

We are sure that you got some ideas and many questions about the incremental model the right way to implement it. Register for a Certified Scrum Master Certification Online and understand practically.