The five development methodologies

Overview

Recall questions on the waterfall lifecycle, agile methodologies, extreme programming, the spiral model and rapid application development, the merits and drawbacks of each, prototypes, and what iterative development means.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is a software development methodology, and why does one matter?

   Model answer

   An organised approach to building software that sets out what stages the work goes through, in what order, who is involved, and how progress and change are handled. It matters because software projects are large, involve many people, and fail far more often through poor organisation, misunderstood requirements and uncontrolled change than through anyone being unable to write the code.

2. 2

   Describe the waterfall lifecycle.

   Model answer

   A sequential model in which the project passes through a fixed series of stages, each completed and signed off before the next begins: feasibility study, requirements analysis, design, implementation, testing, and then installation and maintenance. Each stage produces documentation that feeds the next, and the flow is intended to be one way, like water falling from one step to the next.

3. 3

   State the stages of the waterfall lifecycle in order.

   Model answer

   Feasibility study; requirements analysis; design; implementation (coding); testing; installation, then ongoing evaluation and maintenance. Each stage is completed and approved before the next begins.

4. 4

   What are the merits of the waterfall lifecycle?

   Model answer

   It is simple to understand and to manage, because at any moment everyone knows which stage the project is in. Costs, timescales and staffing can be estimated in advance because the whole scope is fixed at the start. It produces thorough documentation at every stage, which makes long-term maintenance and handover to a different team much easier, and which is often required for auditing or safety certification. It also works well when the requirements genuinely are known and stable, and it needs less continuous customer involvement than the other approaches.

5. 5

   What are the drawbacks of the waterfall lifecycle?

   Model answer

   It assumes the requirements are fully understood before any code is written, which is rarely true. Because the client sees nothing working until near the end, misunderstandings are discovered very late, when they are most expensive to correct. Going back to an earlier stage is difficult and costly, so the model copes badly with changing requirements. Nothing usable is delivered until the whole project is finished, and heavy documentation absorbs time.

6. 6

   Describe agile methodologies.

   Model answer

   A family of approaches in which the software is built in a series of short iterations, each producing a working, tested increment of the product that can be shown to the customer. Requirements are expected to change and are re-prioritised at the start of each iteration in the light of feedback. Working software is valued over comprehensive documentation, and the customer is involved throughout rather than only at the beginning and the end.

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