Agile Model Pros and Cons

What is Agile model – advantages, disadvantages and when to use it?

Agile development model is also a type of Incremental model. Software is developed in incremental, rapid cycles. This results in small incremental releases with each release building on previous functionality. Each release is thoroughly tested to ensure software quality is maintained. It is used for time critical applications. Extreme Programming (XP) is currently one of the most well-known agile development life cycle model.

Diagram of Agile model:

Advantages of Agile model:

§  Customer satisfaction by rapid, continuous delivery of useful software.

§  People and interactions are emphasized rather than process and tools. Customers, developers and testers constantly interact with each other.

§  Working software is delivered frequently (weeks rather than months).

§  Face-to-face conversation is the best form of communication.

§  Close, daily cooperation between business people and developers.

§  Continuous attention to technical excellence and good design.

§  Regular adaptation to changing circumstances.

§  Even late changes in requirements are welcomed

Disadvantages of Agile model:

§  In case of some software deliverable, especially the large ones, it is difficult to assess the effort required at the beginning of the software development life cycle.

§  There is lack of emphasis on necessary designing and documentation.

§  The project can easily get taken off track if the customer representative is not clear what final outcome that they want.

§  Only senior programmers are capable of taking the kind of decisions required during the development process. Hence it has no place for newbie programmers, unless combined with experienced resources.

When to use agile model:

§  When new changes are needed to be implemented. The freedom agile gives to change is very important. New changes can be implemented at very little cost because of the frequency of new increments that are produced.

§  To implement a new feature the developers need to lose only the work of a few days, or even only hours, to roll back and implement it.

§  Unlike the waterfall model in agile model very limited planning is required to get started with the project. Agile assumes that the end users’ needs are ever changing in a dynamic business and IT world. Changes can be discussed and features can be newly effected or removed based on feedback. This effectively gives the customer the finished system they want or need.

§  Both system developers and stakeholders alike, find they also get more freedom of time and options than if the software was developed in a more rigid sequential way. Having options gives them the ability to leave important decisions until more or better data or even entire hosting programs are available; meaning the project can continue to move forward without fear of reaching a sudden standstill.

Intro to Agile Modeling

An Introduction to Agile Modeling

Agile Modeling (AM) is a practice-based methodology for effective modeling and documentation of software-based systems. Simply put, Agile Modeling (AM) is a collection of values, principles, and practices> for modeling software that can be applied on a software development project in an effective and light-weight manner. As you see in Figure 1 AM is meant to be tailored into other, full-fledged methodologies such as XP or RUP, enabling you to develop a software process which truly meets your needs. In fact, this tailoring work has already been done for you in the form of the Disciplined Agile Delivery (DAD) process framework. 

- See more at: http://www.agilemodeling.com/essays/introductionToAM.htm#sthash.xzJr8hw5.dpuf

The values of AM, adopting and extending those of extreme Programming v1, are communication, simplicity, feedback, courage, and humility. The keys to modeling success are to have effective communication between all project stakeholders, to strive to develop the simplest solution possible that meets all of your needs, to obtain feedback regarding your efforts often and early, to have the courage to make and stick to your decisions, and to have the humility to admit that you may not know everything, that others have value to add to your project efforts.

AM is based on a collection of principles, such as the importance of assuming simplicity when you are modeling and embracing change as you are working because requirements will change over time. You should recognize that incremental change of your system over time enables agility and that you should strive to obtain rapid feedback on your work to ensure that it accurately reflects the needs of your project stakeholders. You should model with a purpose, if you don't know why you are working on something or you don't know what the audience of the model/document actually requires then you shouldn't be working on it. Furthermore, you need multiple models in your intellectual toolkit to be effective. A critical concept is that models are not necessarily documents, a realization that enables you travel light by discarding most of your models once they have fulfilled their purpose. Agile modelers believe that content is more important than representation, that there are many ways you can model the same concept yet still get it right. To be an effective modeler you need to recognize that open and honest communication is often the best policy to follow to ensure effective teamwork. Finally, a focus on quality work is important because nobody likes to produce sloppy work and that local adaptation of AM to meet the exact needs of your environment is important.

To model in an agile manner you will apply AM's practices as appropriate. Fundamental practices include creating several models in parallel, applying the right artifact(s) for the situation, and iterating to another artifact to continue moving forward at a steady pace. Modeling in small increments, and not attempting to create the magical "all-encompassing model" from your ivory tower, is also fundamental to your success as an agile modeler. Because models are only abstract representations of software, abstractions that may not be accurate, you should strive to prove it with code to show that your ideas actually work in practice and not just in theory Active stakeholder participation is critical to the success of your modeling efforts because your project stakeholders know what they want and can provide you with the feedback that you require. The principle of assume simplicity is a supported by the practices of creating simple content by focusing only on the aspects that you need to model and not attempting to creating a highly detailed model, depicting models simply via use of simple notations, and using the simplest tools to create your models. You travel light by single sourcing information, discarding temporary models and updating models only when it hurts. Communication is enabled by displaying models publicly, either on a wall or internal web site, through collective ownership of your project artifacts, through applying modeling standards, and by modeling with others. Your development efforts are greatly enhanced when you apply patterns gently. Because you often need to integrate with other systems, including legacy databases as well as web-based services, you will find that you need to formalize contract models with the owners of those systems. Read this article for a better understanding of how AM's practices fit together.

Figure 2. Agile Model Driven Development (AMDD).

I would argue that AM is an agile approach to modeling that at its core AM is simply a collection of practices that reflect the principles and values shared by many experienced software developers. With an Agile Model Driven Development (AMDD) (see Figure 2) approach you typically do just enough high-level modeling at the beginning of a project to understand the scope and potential architecture of the system, and then during development iterations you do modeling as part of your iteration planning activities and then take a just in time (JIT) model storming approach where you model for several minutes as a precursor to several hours of coding.