System Development Life Cycle (SDLC)

• System Development Life Cycle (SDLC) is a structured process used by organizations to design, develop, test, and deploy information systems or software applications.

Phases of SDLC (PSDTDM)

• Planning identifies the needs for a new system or improvements to an existing one.
• Output of planning includes a feasibility report and a project plan.
• System Analysis gathers and analyzes business requirements, defining the system functionalities.
• It involves creating a Data Flow Diagram (DFD) and an Entity Relationship Diagram (ERD).
• Output of system analysis includes a requirement specification document and system models.
• System Design converts requirements into a detailed design.
• It defines the structure/architecture of the system, database, user interface aspects, and security measures.
• It involves specifying hardware and software requirements.
• Output of system design includes a system design, a prototype (capstone), and UI/UX design.
• Development (Implementation) involves developers writing and compiling code based on the design, using programming languages like Java, VB, C#, or Python.
• Output of development is program code or software modules.
• Testing evaluates the system to ensure it functions as expected.
• Types of testing include unit testing (per module), integration testing (integrating modules), system testing (whole system), and user acceptance testing.
• Output of testing are test cases, reports, and bug fixes.
• Deployment is when the system is released for actual use.
• Deployment strategies include direct cutover, parallel, or phased (pilot/routine deployment).
• Output includes the live system, training manuals, and user support.
• Maintenance provides ongoing support, bug fixes, and enhancements.
• Maintenance involves system updates, maintenance reports, and user feedback.

Importance of SDLC

• SDLC provides a structured approach.
• It aids in risk management and cost control.
• It ensures software quality and user satisfaction.
• It promotes efficiency and collaboration.

SDLC Models

• Waterfall Model is a sequential or phase-by-phase approach.
• Agile Model
• Spiral Model
• V-Model focuses on validation and verification
• RAD (Rapid Application Development)

Waterfall Model

• Waterfall model is a sequential or phase-by-phase approach.
• Considered one of the earliest and most structured models of the SDLC.
• Introduced by Winston W. Royce in 1970.
• Phases include requirements gathering & analysis, system design, implementation/development, testing, deployment, and maintenance.

Advantages of Waterfall

• Structured and simple to follow.
• Well-documented.
• Easier to manage.
• Best for small & stable projects.

Disadvantages of Waterfall

• Rigid and inflexible.
• Late testing and feedback.
• Not ideal for complex projects.
• Minimal user involvement.
• Use waterfall for projects with well-defined requirements.
• Suitable for small to medium-sized projects.
• Use for projects with minimal expected changes.
• Good for government or regulatory projects.

Agile Model

• Agile is a kind of integrative and flexible and continuous feedback.
• Modern alternative and flexible approach to software development that focuses on continuous improvement, collaboration, and customer feedback.
• Employs adaptive planning.
• Phases of concept and planning, design, development, testing, release/deployment, feedback, maintenance & review.
• Iterations usually taken 1 to 4 weeks
• Key developers were Kent Beck, Mike Beedle, Arie van Bennekum, Alistair Cockburn, Ward Cunningham, and Martin Fowler

When to use Agile

• If projects have evolving requirements
• Start up and business market adaption
• Continues user and customer feedback is required
• Teams that prioritize flexibility and collaboration

RAD (Rapid Application Development) Model

• Relies on rapid prototype and is faster because of the concurrent model.
• Iterative and adaptive software development methodology that emphasizes quick prototyping & user feedback and fast delivery.
• Introduced in the 1980's by James Martin as an alternative to Waterfall model.
• Phases include requirement planning (capturing initial requirements), user design (developers need to create prototype), rapid construction, and cutover (training, support and maintenance provided).

Characteristics of RAD

• Fast development.
• User involvement.
• Iterative process.
• Minimal documentation.

Advantages of RAD

• Fast delivery
• User Centric
• Flexible
• High Quality Output

Disadvantages of RAD

• Requires skilled Team
• Not suitable for large complex systems
• High user involvement needed
• Difficult to manage large teams

When to use the RAD model

• Projects with fast changing Requirements
• Small to medium sized applications
• Projects where user feedback is critical
• When reusable components or low code tools can be leveraged.

Spiral Model

• Big Project

V Model

• Validation and verification
• Tests occur at all development phases