System Development Life Cycle (SDLC)

• Systems development is creating or modifying business systems.
• Projects range from small to large in fields like stock analysis and video game development.
• Companies can develop systems internally or outsource.
• Outsourcing allows focus on core competencies and uses external expertise.
• It is common for IS projects to overrun budgets and exceed scheduled completion dates.

The System Development Life Cycle (SDLC)

• The SDLC was first described in 1970.
• SDLC is used to design, develop, and test software.
• The SDLC aims to produce high-quality software within time and cost estimates.
• It consists of seven stages and is sometimes called the waterfall method.

SDLC Stages: Stage 1 - Preliminary Investigation/System Investigation

• A systems review committee evaluates requests.
• A committee provides a variety of experience and knowledge.
• Committees prioritize effectively and reduce bias.
• A typical committee includes the IT director and managers from other departments.
• The IT director acts as a technical consultant.
• Communication about the investigation and roles involved is important.
• A systems analyst studies the systems request and recommends action.
• The analyst gathers facts about the problem/opportunity, scope, benefits, time, and costs.
• The end product is a report to management.

Feasibility Analysis

• Economic feasibility: Do the system benefits justify the required time, money, and resources?
• Technical feasibility: Can the system be developed and implemented using existing technology?
• Legal feasibility: Does the system comply with laws, regulations, and contractual obligations?
• Scheduling feasibility: Can the system be developed and implemented in the allotted time?
• Operational feasibility: Does the organization have the people, and will people use the system?
• The goal is to understand the problem or opportunity.
• A key question: "Is the problem worth solving?"
• The deliverable is a feasibility study.

SDLC Stages: Stage 2 - Systems Analysis

• Systems analysis defines problems and opportunities.
• Having complete support of top-level managers is important when focusing on business goals.
• Build a logical model of the new system.
• Use fact-finding techniques like interviews, surveys, document review, observation, and sampling.
• Use the fact-finding results to build business models, data, process, and object models.
• The deliverable is a system requirements document.
• The system requirements document describes requirements, costs, benefits, and development strategies.

SDLC Stages: Stage 3 - System Design

• System design defines how the system will work.
• It determines how the system will meet the business needs.
• The purpose is to create a physical model that satisfies requirements.
• Design of the user interface and identification of outputs, inputs, and processes takes place.
• Internal and external controls, including computer-based and manual features, are designed.
• Experienced programmers decide what programs and databases are needed.
• CASE tools (Computer-Aided Software Engineering) can be used.
• The deliverable is a design specification or a system specification.

SDLC Stages: Stage 4 - System Development

• Programmers write programs and design databases based on approved design specifications.
• Concepts are translated into specifications.
• The new system is developed; components and programs are installed.
• Users must be trained in the new system.

SDLC Stages: Stage 5 - System Testing

• All aspects of performance are tested, and adjustments are made if necessary.
• Unit test: testing individual software units.
• Subsystem test: tested modules are combined into subsystems.
• Subsystem testing catches communication errors among modules.
• System test: testing the entire system to ensure it meets client requirements.
• User test: testing by real users to complete tasks, which helps identify unexpected problems.

SDLC Stages: Stage 6 - Implementation

• Prepares the new system for production use.
• Requires training, change management, and system conversion.

Conversion Methods

• Direct cutover: replacing the old system completely with the new one.
• Pilot conversion: part of the organization switches to the new system.
• Phased conversion: implementing the system in stages.
• Pilot-phased conversion: a combination of pilot and phased, used for complex systems.
• Parallel conversion: running old and new systems simultaneously.
• Systems implementation involves tasks such as assembing defined hardware, software and database, etc.
• The deliverable is a system that its user community can use.

SDLC Stages: Stage 7 - Operation and Maintenance

• The new system is periodically reviewed.
• Modifications are made as needed.
• Project teams assess the system to reduce operation and maintenance costs with error detection.

SDLC: Strengths and Weaknesses

• Provides control over software development.
• Management knows what is being done, who is doing it, and when it should be finished.
• Important when system requirements must be precisely defined.
• Does not handle dynamic needs well.
• Difficult to change anything without reverting to an earlier stage.
• Formal specifications are a poor communication vehicle.
• Problems are often discovered late.

Six Basic SDLC Methodologies

• Waterfall Model: linear and requires phases to be completed in order.
• Iterative Model: focuses on repetition and testing, with new versions produced each phase.
• Spiral Model: flexible.
• The V-model (verification and validation): similar to waterfall model with testing incorporated.
• Big Bang Model: flexible, leaving detailed planning behind; used for broad ideas.
• Agile Model: relatively well-known in software development.