Agile is a methodology that is frequently being used for software development by influential IT organizations around the world. The Agile Development Model represents constant iteration and is somewhat like an Incremental Model. The idea behind the concept is to allow change at any point throughout the lifecycle of the project. There are several other development models actively being employed in the software development sector, but Agile dominates by proving to be more productive and efficient for short spanned projects.

Other Development Models against Agile:

• Waterfall Model
• V Model
• Spiral Model
• Evolutionary Prototype Model
• Incremental Model
• Iterative Model

Agile vs. Waterfall

The Waterfall Development Method is traditional, being the first to originate among it’s kind. It is only second to Agile Development in popularity despite the emergence of others after it. Waterfall implicates a linear workflow; while Agile consists of multiple short-lived lifecycles, it completes a single one. Agile is about repeating of a set of tasks and Waterfall undertakes one task at a time without revisiting it until the end.

Waterfall is a simple step by step methodology, one phase is completed and then the next is begun. There is no going back and forth as in Agile Development because every step is carried out in accordance with a pre-prepared plan. Agile involves very little planning at the starting point because it follows the belief that info or guidelines regarding a virtual objective are inadequate. One can truly understand the concept during the process and build upon it; moreover there’s always room for improvement.

Developers and Testers work as a team in Agile Development, so that issues can be identified and tackled alongside. Waterfall development does not allow testing until the completion of the development process. Thus if any bugs appear, they will be resolved at the end, or if the product doesn’t work as expected, the development process will be reinstated as a whole. Agile lets the customer/client have a say throughout the process multiple times, so change is always welcome and integrated between sessions. With Waterfall model, the project is only open for evaluation and/or comments after completion. Therefore if the respective owner has objections to the final outcome, it will have to be re-done from the beginning over and over again until the desired goal is achieved.

Agile vs. V Model

The V stands for Verification and Validation; it executes tasks in a sequential path, similar to waterfall. It is different from other development models because of certain requirements it comes with. Business and system specifications should be defined for the development process. Also, the testing process is thorough and involves as many stages as the development process.

While some changes are possible along the V-model, it is not as flexible as the Agile model. The code or coding is the center point of this model and forms the bottom of the V. Tests are usually designed at the downward stages, so defects can be visible during the process. However unlike Agile, testing may have to be done all over again to adjust with the changes as they cannot be configured at the spot.

It is usually suitable for old clients who trust the developers’ decisions and the developers in return are accustomed to their ways. Agile can involve the development of several prototypes, whereas V model uses none and is thereby subject to high risk.

Agile vs. Spiral Model

The Spiral Model has a few things in common with the Agile model, due to its iterative manner. Instead of repeating whole cycles, it divides the process into four segments (Planning, Risk analysis, Evaluation and Engineering) that are revisited through a spiral path. Agile produces functional software fast and frequently; Spiral also develops software at early stage, but at lower frequency.

It puts major focus on risk analysis and is therefore suitable for long-term projects. Unlike Agile, it becomes more costly as the spiral widens because the four segments are worked upon independently instead of a collaborative approach.

Agile vs. Evolutionary Prototype Model

Developing software with Agile is basically a breakdown of its components which are designed in different life cycles. Different components are prototyped in a series of lifecycles and put together like building blocks as we progress. Evolutionary Prototype development method forms prototypes of the complete software, which can be called a compound approach. Instead of a sequence of brief life cycles, there are two or more life cycles working side by side. We can assume three versions of the same product being developed by three different teams at the same time. The final products of all the life cycles are then merged at the end.

Agile vs. Incremental and Iterative Model

Incremental software development involves building the product piece by piece. One piece is finished in each life cycle and then all the complete pieces are assembled together at the endpoint. The iterative model also divides the product into pieces, however all the pieces are managed together. Partial features of each piece are developed in harmony through a series of life cycles till completion.

The Agile model is in fact a combination of the Incremental and Iterative model. The product to be developed in divided into smaller parts that may be constructed one by one or in groups. Instead of putting all pieces together at the end, they are integrated with each other during the process.

When to Use Agile:

• When regular changes are anticipated in a project
• When addition of a new feature has no direct or deep effect on the rest of the work
• When pre-planning is not feasible and information is limited
• When the client side and developer side are in constant communication, and are capable of working as a team

Advantages:

• Continuous delivery of functional software
• Increased customer involvement and satisfaction
• Accelerated development Process
• Time and Cost effective
• Rapid adaptation to change or modernization

Disadvantages:

• It can be hard to break down the components of big/lengthy projects
• Lack of detailed planning is problematic in certain cases
• Objectives are exceedingly prone to fall off track
• Demand for abrupt decisions requires experience and intellectual judgement
• Lack of documentation
• Immediate solutions do not work for long term, producing technical debt.