Systems Life Cycle Models

Introduction

There are many different ways of planning and analysing systems. These are known as methodologies. Each methodology has advantages and disadvantages and is suited for a specific purpose. For example, the waterfall methodology is suited for software development.

While they are different, they all aim to do produce the following:
  1. Definition
  2. Investigate and analysis
  3. Design
  4. Implementation
  5. Testing
  6. Installation/ Deployment
  7. Documentation
  8. Evaluation
  9. MaintenanceSDLC Overview Model
You will need to analyse and reflect on each of these methodologies to provide advantages and disadvantages. If possible you should link these to your workplace.

You can learn more about the concepts of systems design and analysis using the link below:

Learner Presentations

Below you will find the presentation that you created that detail the Waterfall, Spiral, Agile and V Shape Methodologies:

Waterfall

The waterfall Model illustrates the software development process in a linear sequential flow. This means that any phase in the development process begins only if the previous phase is complete. Each phase has a dependency on the previous phase. The waterfall approach does not define the process to go back to the previous phase to handle changes in requirement. 

Each phase is ordered in sequence and phases do not overlap.

SDLC Waterfall

Spiral

The spiral model has four phases: Planning, Risk Analysis, Engineering and Evaluation. A software project repeatedly passes through these phases in iterations (called Spirals in this model). In the baseline spiral, starting in the planning phase, requirements are gathered and risk is assessed. Each subsequent spirals builds on the baseline spiral. This allows for reflection to occur through each phase, providing quality assurance.

When to use Spiral model:
  • When costs and risk evaluation is important
  • For medium to high-risk projects
  • Long-term project commitment unwise because of potential changes to economic priorities
  • Users are unsure of their needs
  • Requirements are complex
  • New product line
  • Significant changes are expected (research and exploration)


Agile

There are different forms of agile development methodology, a popular one being Scrum. As the name suggests it promotes flexibility and the concept of sprints. The aim being that development time is reduced while still ensuring that quality is maintained.

The Scrum framework in 30 seconds:
  1. A product owner creates a prioritized wish list called a product backlog.
  2. During sprint planning, the team pulls a small chunk from the top of that wish list, a sprint backlog, and decides how to implement those pieces.
  3. The team has a certain amount of time — a sprint (usually two to four weeks) — to complete its work, but it meets each day to assess its progress (daily Scrum).
  4. Along the way, the Scrum Master the team focused on its goal.
  5. At the end of the sprint, the work should be potentially shippable: ready to hand to a customer, put on a store shelf, or show to a stakeholder.
  6. The sprint ends with a sprint review and retrospective.
  7. As the next sprint begins, the team chooses another chunk of the product backlog and begins working again.
SDLC Agile

V-Shape

V- model stands for Verification and Validation model. Just like the waterfall model, the V-Shaped life cycle is a sequential path of execution of processes. Each phase must be completed before the next phase begins. Testing of the product is planned in parallel with a corresponding phase of development.
SDLC V-Shape

Hybrid

Methodologies can be combined to meet a specific need or allow for flexibility that a single methodology might not be able to provide.

Hybrid SDLC

Additional Links

You can find additional information about these life cycle models below. Ensure that you appropriately reference any materials that you use.
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