Software Development Methodologies(Waterfall, Agile,Iterative,Spiral & Scrum)

Software development methodology is a framework that is used to structure, plan, and control the process of developing an information system - this includes the pre-definition of specific deliverables and artifacts that are created and completed by a project team to develop or maintain an application.



A wide variety of such frameworks have evolved over the years, each with its own recognized strengths and weaknesses. One software development methodology framework is not necessarily suitable for use by all projects. Each of the available methodology frameworks are best suited to specific kinds of projects, based on various technical, organizational, project and team considerations



Every software development methodology framework acts as a basis for applying specific approaches to develop and maintain software. Several software development approaches have been used since the origin of information technology.

Waterfall development

The Waterfall model is a sequential development approach, in which development is seen as flowing steadily downwards (like a waterfall) through the phases of requirements analysis, design, implementation, testing (validation), integration, and maintenance. The first formal description of the method is often cited as an article published by Winston W. Royce in 1970

• Project is divided into sequential phases, with some overlap and splashback acceptable between phases.

• Emphasis is on planning, time schedules, target dates, budgets and implementation of an entire system at one time.

• Tight control is maintained over the life of the project via extensive written documentation, formal reviews, and approval/signoff by the user and information technology management occurring at the end of most phases before beginning the next phase.

Pitfalls of Waterfall model:

This model does not suitable for non-trivial project to finish a phase of a software product's lifecycle perfectly before moving to the next phases and learning from them.

Designers may not be aware of future implementation difficulties when writing a design for an unimplemented software product which result

Agile Development

Agile software development is a group of software development methodologies based on iterative and incremental development, where requirements and solutions evolve through collaboration between self-organizing, cross-functional teams. It promotes adaptive planning, evolutionary development and delivery, a time-boxed iterative approach, and encourages rapid and flexible response to change. It is a conceptual framework that promotes foreseen interactions throughout the development cycle.

Agile methods break tasks into small increments with minimal planning and do not directly involve long-term planning. Iterations are short time frames (timeboxes) that typically last from one to four weeks. Each iteration involves a team working through a full software development cycle, including planning, requirements analysis, design, coding, unit testing, and acceptance testing when a working product is demonstrated to stakeholders. This minimizes overall risk and allows the project to adapt to changes quickly. Stakeholders produce documentation as required. Iteration might not add enough functionality to warrant a market release, but the goal is to have an available release (with minimal bugs) at the end of each iteration. Multiple iterations might be required to release a product or new features.

Team composition in an agile project is usually cross-functional and self-organizing, without consideration for any existing corporate hierarchy or the corporate roles of team members. Team members normally take responsibility for tasks that deliver the functionality iteration requires. They decide individually how to meet iteration’s requirements.

Agile methods emphasize face-to-face communication over written documents when the team is all in the same location. Most agile teams work in a single open office (called a bullpen), which facilitates such communication. Team size is typically small (5-9 people) to simplify team communication and team collaboration. Larger development efforts can be delivered by multiple teams working toward a common goal or on different parts of an effort. This might require a coordination of priorities across teams. When a team works in different locations, they maintain daily contact through videoconferencing, voice, e-mail, etc.





Pitfalls of Agile Model:

An agile software development method is that it is developer-centric rather than user-centric. Agile software development focuses on processes for getting requirements and developing code and does not focus on product design.

Iterative and incremental development

Iterative and Incremental development is at the heart of a cyclic software development process developed in response to the weaknesses of the waterfall model. It starts with an initial planning and ends with deployment with the cyclic interactions in between.

Incremental development slices the system functionality into increments (portions). In each increment, a slice of functionality is delivered through cross-discipline work, from the requirements to the deployment. The unified process groups increments/iterations into phases: inception, elaboration, construction, and transition.



• Inception identifies project scope, risks, and requirements (functional and non-functional) at a high level but in enough detail that work can be estimated.

• Elaboration delivers a working architecture that mitigates the top risks and fulfills the non-functional requirements.

• Construction incrementally fills-in the architecture with production-ready code produced from analysis, design, implementation, and testing of the functional requirements.

• Transition delivers the system into the production operating environment.



Each of the phases may be divided into 1 or more iterations, which are usually time-boxed rather than feature-boxed. Architects and analysts work one iteration ahead of developers and testers to keep their work-product backlog full.

How Agile methodology differ from Iterative

Most agile methods share iterative development's emphasis on building releasable software in short time periods. Agile methods differ from iterative methods in that their time period is measured in weeks rather than months. Most agile methods also differ by treating their time period as a strict timebox.

Spiral development

The spiral model is a software development process combining elements of both design and prototyping-in-stages, in an effort to combine advantages of top-down and bottom-up concepts. It is a meta-model, a model that can be used by other models.

The basic principles are:

• Focus is on risk assessment and on minimizing project risk by breaking a project into smaller segments and providing more ease-of-change during the development process, as well as providing the opportunity to evaluate risks and weigh consideration of project continuation throughout the life cycle.

• "Each cycle involves a progression through the same sequence of steps, for each part of the product and for each of its levels of elaboration, from an overall concept-of-operation document down to the coding of each individual program."

• Each trip around the spiral traverses four basic quadrants: determine objectives, alternatives, and constraints of the iteration; evaluate alternatives; Identify and resolve risks; develop and verify deliverables from the iteration; and plan the next iteration.

• Begin each cycle with an identification of stakeholders and their win conditions, and end each cycle with review and commitment.

Scrum Methodology

Scrum is an iterative, incremental framework for project management often seen in agile software development, a type of software engineering.

Sprint

A sprint is the basic unit of development in Scrum. Sprints tend to last between one week and one month, and are a "timeboxed" (i.e. restricted to a specific duration) effort of a constant length. Each sprint is preceded by a planning meeting, where the tasks for the sprint are identified and an estimated commitment for the sprint goal is made, and followed by a review or retrospective meeting, where the progress is reviewed and lessons for the next sprint are identified. During each sprint, the team creates a potentially deliverable product increment.

Scrum enables the creation of self-organizing teams by encouraging co-location of all team members, and verbal communication between all team members and disciplines in the project.

Scrum teams consist of three core roles and a range of ancillary roles

Core roles

The core roles in Scrum teams are those committed to the project in the Scrum process—they are the ones producing the product (objective of the project).

Product Owner

The Product Owner represents the voice of the customer and is accountable for ensuring that the Team delivers value to the business. The Product Owner writes customer-centric items (typically user stories), prioritizes them, and adds them to the product backlog. Scrum teams should have one Product Owner, and while they may also be a member of the Development Team, it is recommended that this role not be combined with that of ScrumMaster.

Team

The Team is responsible for delivering the product. A Team is typically made up of 5–9 people with cross-functional skills who do the actual work (analyse, design, develop, test, technical communication, document, etc.). It is recommended that the Team be self-organizing and self-led, but often work with some form of project or team management.

ScrumMaster

Scrum is facilitated by a ScrumMaster, also written as Scrum Master, who is accountable for removing impediments to the ability of the team to deliver the sprint goal/deliverables. The ScrumMaster is not the team leader but acts as a buffer between the team and any distracting influences. The ScrumMaster ensures that the Scrum process is used as intended. The ScrumMaster is the enforcer of rules. A key part of the ScrumMaster’s role is to protect the team and keep them focused on the tasks at hand. The role has also been referred to as a servant-leader to reinforce these dual perspectives.

Ancillary roles

The ancillary roles in Scrum teams are those with no formal role and infrequent involvement in the Scrum process—but nonetheless, must be taken into account.

Stakeholders (customers, vendors)

These are the people who enable the project and for whom the project will produce the agreed-upon benefit[s], which justify its production. They are only directly involved in the process during the sprint reviews.

Managers (including Project Managers)

People who will set up the environment for product development.