Agile Software Architecture Written By Christine Miyachi

This article by Phillip A. Laplante and Colin J. Neill of Penn State University explores the rumors of the demise of the waterfall model. The Waterfall process model progresses software products linearly from conception, through requirements, design, code, and test (Neill, 2004). The Waterfall method was developed in 1970 by Winston Royce when computer systems were monolithic, number-crunching entities with rudimentary front ends and users’ needs were filtered through the partisan minds of the computer illuminati building the systems (Neill, 2004). Most systems built in that time did not pay much attention to input from stakeholders, which is a good environment for the Waterfall method to work in – an environment where requirements seldom change after specification due to the fact that users are not involved in the development and therefore cannot provide feedback regarding incorrect assumptions or missing features (Neill, 2004).

“Agile” was first introduced in 2001, by a team of software engineers looking to improve their adaptiveness and responsiveness to ever-changing requirements. Not knowing where to begin, the team began by formulating principles, which they would use to guide their new development process. Which, in turn, lead to the creation of the Agile Manifesto, and thus a new methodology was born.

Agile is an iterative and incremental (evolutionary) approach to software development which is performed in a highly collaborative manner by self-organizing teams within an effective governance framework, with "just enough" ceremony, that produces high quality solutions, in a cost effective and timely manner which meets the changing needs of its stakeholders [1].

The waterfall model was legally introduced as an idea through a paper that had been published by a man called Winston Royce in the year 1970. However, due to the waterfall model being introduced by Winston Royce himself, it had been introduced as an example of a flawed software development method, which was vulnerable due to its shortcomings. The waterfall model philosophy had been inherited from the hardware manufacture and construction strategies that had been in practice in the year 1970s; therefore it had a structured approach to the software development itself. In comparison to the agile methodology, which developed in the year 1990s where the developers had decided to break away from the traditional structured, segmented and administrative approaches, which were being made to the developed software, and progressed towards more of the flexible development styles. The term Agile can be referred to as being lightweight methods, which had been declared in a research paper in the year 1974 by Edmonds. Furthermore, some of the most noticeable and common agile methods of the software development that subsequently had been evolved were known as Scum in the year 1995, 'Extreme Programming ' in 1996, 'Adaptive Software Development ', 'Dynamic Systems Development Method ' in 1995 and 'Feature Driven Development '. In the year 2001, a team of developers in the agile software development had declared the agile manifesto. The agile

SC will compare traditional and various iterative implementations of the SDLC. For example, Braude and Bernstein (2011) state that the popular and mature waterfall process model promotes simple comprehension, project management, and resource distribution of small project development lifecycles. The serial nature of the traditional SDLC leans toward the gathering of all requirements at the beginning of the project whereas the majority of testing occurs at the end of the lifecycle. The waterfall model’s linear design creates disastrous risks for large projects if the project team does not understand the core requirements during the initial phase of the project or the detection of major problems occurs toward the end of the project. On the other hand, a spiral model significantly reduces risks for large projects whereas complexity causes overkill for smaller projects. The project’s physical scope, timeline, budget, and resource determine which the most optimal process model for a project. Table 1.1 displays a comparison chart that SC uses to weigh advantages and disadvantages of traditional SDLC and Agile development methodologies. SC will utilize this chart to determine which development methodology is utilized based on the primary amount of questions answered positively weighed with the clients business case requirements. “Agile software development is a

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In the year of 2001 many proponents met in Utah and came to discuss and agree on underlying principles (Hoffer, George, & Valacich, 2011). Through this discussion they came up with the “The Agile Manifesto” (Hoffer, George, & Valacich, 2011). There is

At the Trinidad Gas Company (TGC), software development is done using an adaptive version of the Waterfall Methodology and the US Department of Justice Systems Development Life Cycle. The stages used by TGC in this mainly Waterfall Method involves the Initiation Phase, System Concept Development Phase, Planning Phase, Requirements Analysis Phase, Design Phase, Development Phase, Integration and Test Phase, Implementation Phase and Operations and Maintenance Phase. This methodology is a predictable, rigid and sequential design process, which means, that as each of the nine stages are completed, the developers move on to the next stage. In this sequential process there also exists a stage gate between each stage. This stage gate is simply a review of the project status to determine if to proceed or not. However, the stage gate approach is not always followed on many of the development projects undertaken by TGC. A brief description of each stage is mentioned below:

An early and often cited paper by Adrion (1993, cited in Flint 2009, p. 229 - 230) presents engineering method as one of software engineering research method. It is necessary to utilize engineering method in this study in order to observe existing solutions, propose better solutions, build or develop, measure and analyse, and repeat until no further improvements are possible.

The original Waterfall model has a foundation that is supported by two distinct characteristics. First, the methodology is rooted in the fact that that the software be developed in stages. “Originally created by Benington in 1956 and later modified by Royce in 1970, the quintessential Waterfall model is linear and sequential in evolution, typically with milestones at each phase of development. (Pavolka, 2005). As seen in figure 1 (Ruparelia, May 2010), the typical thresholds consisted of Evaluation, Requirements, Analysis, Design, Development, Validation, and ultimately Deployment. The evaluation phase, at the aggregate level, helps to reveal the situation at hand. The requirements phase is arguably the most important phase of the Waterfall plan as it lays out the project statement and sets the framework and expectations for the project. The next phase, Analysis, works as a comparison between what capabilities are needed versus what constraints currently exist. That leads into the Design phase in which the software developers determine the architecture required to meet the customer’s expectations taking into account the constraints previously identified. Development is the next phase that takes the inputs from the Design phase and outputs a tangible product ready for testing. The testing or Validation phase is the process in which the software is checked for two things: a) any and all bugs are identified and removed and b) the original scope of work including all

There are many agile methodologies and frameworks. Some of them are discipline agile delivery (DAD), scaled agile framework (SAFe), scrum, kanban, Extreme programming (XP), dynamic system development method (DSDM), test-driven development (TDD), team software process (TSP) etc.

Software development is one of the highest demands in all over the world. We use software development techniques to solve the problems and to satisfy customers. Agile software development is a conceptual framework for software; it is also a group of software development methods based on iterative development. In 2001, agile software development was created by seventeen people with a desire to find alternative approaches to software development. The most important thing about agile methods are team work, conveying information to the team, face to face conversation, and satisfy the customer. There are various methodologies but I am going to describe the most popular ones.

The waterfall model of software engineering for the systems development life cycle model is the most popular version. Often considered classic approach to life cycle of systems development , linear and sequential waterfall model describes the development system. Waterfall development objectives are different for each stage of a development .Imagine a waterfall on the cliff of an alp. Water has flowed over the edge of a steep mountain side and has started walking down , it cannot turn back. It is same as the waterfall development. Once a phase of development is completed, there is no turning back when the development proceeds to the next phase.

As a result of these weaknesses of the waterfall model, the spiral model was developed which emphasizes iterations of the phases with each phase producing on early Prototype representing a part of the overall system. This helps in demonstrating a proof of concept early in development. This model is similar to the incremental model, but with more emphasis placed on risk analysis. A software project repeatedly passes through these phases in iterations (called spirals in this model). The baseline spiral, starting in the planning phase, requirements are gathered and risk is assessed. Each subsequent spirals builds on the baseline spiral.