Software Development Life Cycle Models

Have you ever thought that the notion “life cycle” can refer not only to living beings? Everything has a life cycle: organizations, brands, machines, and even software. In today’s article, we will talk specifically about such a life cycle and its models. We will tell you what the life cycle is, what models are used more often and which model is the best one for developing your product.

 

What is a software development life cycle?

 

The software development life cycle (SDLC) is a process that begins from the moment you decide to develop a product and ends when this product is completely removed from service.

 

Stages of software development life cycle

 

These models in particular determine the development stages of a new product, its sequence and cyclicality. Still, five main stages of the life cycle have their place in each model:

 

• Requirements planning and analysis
   At this stage, the client’s requirements for the final product are discussed, analyzed, and adjusted. As a result, the parties come to a common decision (this is an extremely important stage since the project requirements are the determining factor when choosing a model);
  

 

• Designing of architecture
  Most technical issues are solved at this stage, for example, which technologies are better to use to develop a specific application, or how frontend and backend components should interact with each other, etc.;
  

 

• Development
  Programmers begin to write code based on the requirements defined earlier;
  

 

• Testing
  At this stage, QA engineers look for inconsistencies with customer requirements in a developed product and report them to developers for revision;
  

 

• Deployment
  It is the stage of transmission of the project code into working condition on a specific machine, adaptation, launch and testing on a new machine.

 

There are five basic models of the development life cycle to facilitate the planning of design, development and release of a quality product:

 

• Waterfall;
• Iterative;
• V-model;
• Agile;
• Spiral.

 

SDLC Waterfall model

 

Each stage of the project is carried out once and in strict sequence. In order to begin a new stage, it is necessary to complete the previous one.

 

The sequence of stages in the Waterfall model is as follows:

 

 

The sequence of stages in the Waterfall model

 

Pros and Cons of Waterfall model

Pros:

 

• the model is easy to understand and apply;
• easy to identify key development points;
• easy to classify and prioritize tasks;
• perfect for short and medium-term projects, with clear, not changing requirements.
  
  

 

Cons:

 

• you cannot go back to the previous stages to make changes to the project;
• product can be released only when it passes all stages;
• the model does not provide activities aimed at risk analysis;
• not suitable for long-term projects where changes may be required at any stage.

 

Iterative development model

 

According to this model, the software is developed in a linear sequence of stages, but in several iterations. Thus, product improvements are planned and take place throughout the entire development life cycle.

 

The sequence of stages during development, in this case, will look like this:

 

 

The sequence of stages in Iterative model

 

Pros and Cons of Iterative model

 

Pros:

 

• changes and new requirements can be introduced gradually;
• it is possible to control the course of development;
• risks associated with costs and schedule compliance can be reviewed;
• if necessary, the product can be released with minimal functionality after the first delivery;
• the model is perfect for developing products that require constant updates.

 

Cons:

 

• intermediate and final delivery dates may be delayed due to limited resources;
• if many changes are often made, the structure of the system may be disrupted.

 

SDLC V-model

 

This model has become a follower of the Waterfall model, but with its help you can eliminate the defects that were missed earlier. In this model, processes are monitored at all stages to ensure the possibility of moving to the next level. The testing process begins at the stage of writing requirements.

 

Stages in the development of a V-shaped model:

 

 

The sequence of stages in v-model

 

Pros and Cons of V-model

 

Pros:

 

• strict stages;
• optimized time management;
• minimal risks since testing starts at the earliest stages.

 

Cons:

 

• there are no actions aimed at risk analysis;
• long development process often leads to the fact that the customer may have no need for a product;
• product can be released only when it passes all the stages.

 

SDLC Spiral model

 

In this model, the product’s life path is like a spiral, which gets unwound from the planning stage, and with the passage of every further step. Thus, at the exit from another round, we get a ready-tested prototype that complements the existing assembly. If the prototype meets all the requirements, it can be released.

 

Illustration of the spiral model development process:

 

 

The sequence of stages in Spiral model

 

Pros and Cons of Spiral model

 

 

Pros:

 

• possible flexibility of design;
• additional functionality can be added at later stages;
• special attention is paid to risk management;
• the model is perfect for large projects.

 

Cons:

 

• change of requirements may cause delays in product development;
• delays and changes in requirements entail additional costs.

 

Agile Model

 

This is a set of different approaches to software development. These approaches are focused on the use of the iterative development (iterations are called sprints in Scrum), the dynamic formation of requirements and ensuring their implementation because of constant interaction within self-organizing working groups. Such groups mainly consist of specialists in various fields. Each individual iteration is a miniature software project. One of the main ideas of Agile is flexibility and interaction both within the team and personally with the customer.

 

The development process for the classic Agile methodology is as follows:

 

The workflow in Agile

 

Pros and Cons of Agile

 

Pros:

 

• fast decision making as the model involves constant communication and quick response;
• flexibility;
• minimal risks;
• less paperwork.

 

Cons:

 

• lots of meetings may slow down the development process;
• It is difficult to get the processes going due to frequent changes in requirements.

 

In modern practice, there is a bigger variety of software development models, which we will tell you about in our future articles. To sum everything up, we can say that there is no one and only model for all projects. Methodologies overlap in terms of resources and are partially similar to each other. In order to make the right choice, it is necessary to take into account the project requirements, funding opportunities, time frames, etc.