System Development Life Cycle

Learning Outcomes

At the end of this topic, students should be able to:

• Understand the System Development Life Cycle
• Describe the steps in SDLC
• Understand system development methodologies

Introduction to SDLC

The Systems Development Life Cycle (SDLC) is like a house project or building a home where the first step is to come up with an idea (or the information system), then the idea is transformed into a drawing that is shown to the customer or owner of the project. This drawing or building plan undergoes several modifications or improvements till the customer agrees to the plan.

SDLC is the process of understanding how an Information System (IS) can support business needs by designing a system, building it, and delivering it to users. The key person in the SDLC is the systems analyst, who analyses the business situation, identifies opportunities for improvements, and designs an information system to implement them.

The SDLC has a similar set of four fundamental phases: planning, analysis, design, and implementation. However, different projects might adopt and emphasize different parts of the SDLC or approach the phases in different ways, but all projects have elements of these four phases.

Each phase is itself composed of a series of steps, which rely upon techniques that produce deliverables (specific documents and files that provide understanding about the project).

Two Key Points About SDLC

i. The phases and steps through which IS projects move, and some of the techniques that produce certain deliverables. ii. The SDLC is a process of gradual refinement.

The deliverables produced in the analysis phase provide an insight to the shape of the new system. These deliverables are used as input to the design phase, which refines them to produce a set of deliverables describing in much more detailed terms exactly how the system will be built. These, in turn, are used in the implementation phase to produce the actual system.

System life cycle is an organizational process of developing and maintaining systems. It is a step-by-step approach to solving business problems. It helps in establishing a system project plan, because it gives an overall list of processes and sub-processes required for developing a system.

Phases and Steps of SDLC

The stages of SDLC suggest a four-phase and seven-steps logical path of any project from start to finish. Project teams may move through the steps consecutively, incrementally, iteratively, or in other patterns.

Four Phases: Planning, Analysis, Design, Implementation

Seven Steps:

1. Project Planning
2. Requirements & Analysis
3. Design
4. Coding & Implementation
5. Testing
6. Deployment
7. Maintenance

flowchart TD
    A[1. Project Planning] --> B[2. Requirements & Analysis]
    B --> C[3. Design]
    C --> D[4. Coding & Implementation]
    D --> E[5. Testing]
    E --> F[6. Deployment]
    F --> G[7. Maintenance]

Phases of the SDLC: Summary Table

System Development Methodologies

A methodology is a formalized approach to implementing the SDLC, it includes a list of steps and deliverables.

Categories of System Methodologies

Process-Centred Methodology

Emphasizes process models as the core of the system concept. It focuses on business processes or the data that support the business.

• Example: Would focus first on defining the processes (e.g., assemble sandwich ingredients).

Data-Centred Methodology

Emphasizes data models as the core of the system concept. Would focus first on defining the contents of the storage areas (e.g., refrigerator) and how the contents were organized.

Object-Oriented Methodology

Attempts to balance the focus between process and data by incorporating both into one model. Would focus first on defining the major elements of the system (e.g., sandwiches, lunches) and look at the processes and data involved with each element.

Structured Design

Structured design methodologies adopt a formal step-by-step approach to the SDLC that moves logically from one phase to the next.

Popular methods include:

• Structured Analysis: traditional method
• Object-Oriented Analysis and Design: widely used newer strategy

SDLC Models

Waterfall Model

The waterfall model is a linear and sequential design process in which progress is seen as flowing steadily downwards (like a waterfall).

• Each phase must be completed before the next one begins
• Possible to go backward (e.g., design → analysis), but extremely difficult

Strengths: Simple, easy to understand, well-suited for projects with clear requirements.

Weaknesses: Inflexible, difficult to accommodate changes, high risk if initial requirements are not well-understood.

Best for: Projects with well-defined requirements and low uncertainty.

flowchart TD
    A[Planning] --> B[Requirements & Analysis]
    B --> C[Design]
    C --> D[Development / Implementation]
    D --> E[Testing]
    E --> F[Deployment]
    F --> G[Maintenance]

Validation and Verification Model (V-Model)

A V-Model is an extension of the Waterfall model that includes corresponding testing phases for each development stage.

• Emphasizes verification and validation
• Ensures early detection of defects
• Like Waterfall, can be rigid and challenging to handle changes

Best for: Projects where quality and reliability are critical.

flowchart LR
    A[Requirements] --> B[System Design]
    B --> C[Architecture Design]
    C --> D[Module Design]
    D --> E[Coding]
    E --> F[Unit Testing]
    F --> G[Integration Testing]
    G --> H[System Testing]
    H --> I[Acceptance Testing]
    A -.->|validates| I
    B -.->|validates| H
    C -.->|validates| G
    D -.->|validates| F

Rapid Application Development (RAD)

RAD is a software development methodology which favours iterative development and the rapid construction of prototypes instead of large amounts of up-front planning. It emerged in the 1990s.

• Planning is interleaved with writing the software itself
• Lack of extensive pre-planning allows software to be written much faster
• Makes it easier to change requirements

Process:

1. Develop preliminary data models and business process models using structured techniques
2. Verify requirements using prototyping to refine data and process models
3. Repeat iteratively until a "combined business requirements and technical design statement" is produced for constructing new systems

flowchart LR
    A[Business\nModelling] --> B[Data\nModelling]
    B --> C[Process\nModelling]
    C --> D[Application\nGeneration]
    D --> E[Testing &\nTurnover]
    E --> A

Iterative Model

This model develops the system through repeated cycles (iterations), allowing refinement through each iteration.

Strengths: Flexible, allows for changes and refinements, reduces risk through early iterations.

Weaknesses: Can lead to scope creep, requires careful project management.

Best for: Complex projects where requirements may evolve over time.

flowchart TD
    A[Requirements] --> B[Analysis]
    B --> C[Design]
    C --> D[Implementation]
    D --> E[Testing]
    E --> F{Complete?}
    F -->|No - next iteration| A
    F -->|Yes| G[Review & Release]

Spiral Model

The Spiral Model combines iterative development with risk assessment. Each iteration involves planning, risk analysis, engineering, and evaluation.

Based on the unique risk patterns of a given project, the spiral model guides a team to adopt elements of one or more process models (incremental, waterfall, or evolutionary prototyping).

Strengths: Focuses on risk management, iterative refinement, and client feedback.

Weaknesses: Inability to manage complex projects simply, requires significant risk assessment expertise.

Best for: Large, high-risk projects where risk management is a priority.

flowchart TD
    A[Plan] --> B[Risk Analysis]
    B --> C[Engineering / Build]
    C --> D[Evaluate]
    D --> A

[Full spiral diagram, see page 6] Original spiral image saved at SDLC-pages/pages/page-6.png.

Agile Model

Agile methodology emphasizes flexibility, collaboration, and customer feedback. Uses iterative cycles called sprints to develop system increments.

Strengths: Highly flexible, adaptive to changes, focuses on customer satisfaction.

Weaknesses: Requires strong team collaboration, can be challenging in fixed-budget projects.

Best for: Dynamic projects where requirements are expected to change frequently.

Other Methodologies

• Prototyping
• Extreme Prototyping
• DevOps
• Scrum

System Analyst

A system analyst is a professional who specializes in analyzing, designing, and implementing information systems. They act as a bridge between business problems and technology solutions, ensuring that business needs are met with appropriate technical solutions.

System analysts work to:

• Improve system efficiency
• Integrate new technologies
• Enhance business processes through effective use of information systems

Homework

Write on the Roles and Responsibilities, Skills, and Types of a System Analyst.

Review Questions

i. Describe the major phases in SDLC. What are the deliverables of each phase? ii. In what ways are the phases related? iii. What major roles does the project manager and system analyst play in building an information system? iv. What are the major roles played by the system analyst on a project team?