Article Summary

1. The Waterfall Model

The Waterfall model, introduced by Winston Royce in 1970, was the predominant software development model until the early 1980s. Its core concept involves simplifying problems by separating function implementation from design, facilitating specialized collaboration. It divides the software lifecycle into six basic activities - planning, requirement analysis, software design, programming, testing, and maintenance - with a fixed and cascading sequence.

Distinctive features of the Waterfall model include:

• Dividing the software project into distinct development phases such as requirement analysis, design, coding, and testing, with clearly defined inputs and outputs for each stage.
• Emphasizing process documentation, which becomes more important than the code itself, as software prototypes appear only in the later stages of development.
• Defining each development stage as a black box to focus developers on their tasks, though this can lead to varying levels of understanding of client requirements and resistance to requirement changes.
• The management documents produced are easily understandable in terms of project progress, making the model favorable to managers but restrictive for developers.
• It implies a no-return approach, where any rework can be costly, particularly if bugs from early stages are found later on.
• The model is best suited for large projects with stable requirements.

However, the Waterfall model has notable limitations, such as minimal feedback between stages, visibility of results only in the late stages of the project lifecycle, and its inability to adapt to changing user requirements.

2. Agile Development

Agile development emerged in the 1990s as a response to rapidly changing requirements, emphasizing close collaboration between developers and business experts, face-to-face communication, frequent delivery of new software versions, and the importance of individuals in the development process. Agile Modeling adds a fifth value of humility to the four values from Extreme Programming (XP): communication, simplicity, feedback, and courage.

Characteristics of Agile development include:

• Speed in adaptation to the fast-paced societal changes, involving more personal and creative thinking.
• Customer involvement as a crucial element, with customers being the end-users and experts in business understanding.
• Focus on the software product rather than documentation, with the latter serving the development rather than being the main focus.
• Thorough design for software quality without outweighing implementation.
• Iteration and small version releases to quickly showcase functionalities and address complex customer requirements.

Agile development priorities include:

• Individuals and interactions over processes and tools.
• Working software over comprehensive documentation.
• Customer collaboration over contract negotiation.
• Responding to change over following a plan.

The Agile approach works best with smaller teams, with size being a critical factor as larger teams may find face-to-face communication challenging.