The Phases of SDLC

Table of Contents

Introduction

This chapter lists the seven phases of SDLC, as identified by the BCS (The UK Chartered Institute for IT), and explains the key aspects of each phase.

The seven phases of SDLC

1. Feasibility study

This first phase is intended ensure it is a good idea to proceed with a project, before too much work is done. It should answer questions like:

  • Is the project practical?
  • Is the project technically possible?
  • Can it be done within a certain timeframe?
  • What is the budget? Is it affordable?
  • Will there be demand for the product? How much revenue will it generate?
  • Is it legal? Will the product break any laws (e.g. privacy / data protection)?

This phase is all about making prediction, which is a risky business. Therefore, answers to these questions will often come with assumptions and caveats (e.g. "We assume we can build this with X staff members, so it will cost £Y. If we need to hire 20% more staff it will cost £Z").

2. Requirement analysis

This phase should provide a detailed understanding of what is needed to make the project a success. It involves 3 steps: gathering, analysing and recording requirements.

This phase should create a set of specifications by which the final product can be measured.

Gathering requirements:

  • Reviewing previous projects
  • Looking at existing documentation
  • Interview stakeholders (colleagues, clients, users, etc...)

Analysing requirements:

  • Create clear, complete, and consistent requirements
  • Resolve conflict between requirements (e.g. the client wants the product in 3 months, but the team wants 6 months to build it)

Record requirements:

  • Create a single summary or list of requirements
  • Write user cases
  • Write user stories
  • Create a process specification
  • Build prototypes of possible solutions

3. Design

The design phases is not just about how the product will look (UI, branding, etc...). It is more designing/ structuring the code.

It involves designing:

  • System architecture - what is the Object Oriented / class structure of the system?
  • System logic - what algorithms / data structures will be used?
    • Abstract representation of data flows
    • Abstract model of the system
    • Includes entity relationship diagrams
  • Physical aspects:
    • What are the inputs and outputs of the system
    • UI
    • Data design (maybe database structure)
    • Process design (how will the team work)

4. Development

The actual programming bit.

This involves implementing design documentation by writing code.

5. Testing

This phase should provide a degree of confidence in the system. It ensures the system:

  • Matches requirements
  • Responds correctly to all agreed inputs
  • Works within time constraints
  • Is sufficiently usable.
  • Runs in intended environments
  • Satisfies stakeholders

6. Implementation

The implementation phase includes launching the product for public use. This involves deploying code to the production environment / servers. This is work is often carried out with/ by DevOps specialists.

A final public launch is often precursed by alpha and beta releases.

7. Maintenance

There 3 main types of maintenance:

  1. Keeping the system running
    • Creating backups
    • Handling demand/ traffic spikes
    • etc...
  2. Fixing bugs:
    • Analysing crash reports
    • Fixing errors
  3. Making enhancement:
    • Improving existing functionality
    • Adding new features

Almost all systems will require all of these types of maintenance.

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