System Development Life Cycle
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System Development Life Cycle
Table of Contents
Overview of System Development Lifecycle
Models of System Development Lifecycle
Waterfall Model
Spiral Model
Rapid Application Development Model
Phases of System Development Life Cycle
Systems Development Lifecycle in Practice – A Case Study
Overview
Phase 1 – Planning
Phase 2 – Analysis
Phase 3 – Design
Phase 4 – Implementation
Phase 5 – Support and Maintenance
Conclusion
References
Overview of System Development Life Cycle
A system development lifecycle (SDLC) is a general process for developing information systems. It provides a framework for the tools, techniques and methods needed to build and implement systems that adequately address business needs. Most SDLC models incorporate fundamental principles which should underpin all systems development (Whitten et al, 1989, pp81-85). These principles include:
The system is for the end-user
Establish phases and tasks
Systems Development is not a sequential process
Systems are capital investments
Dont be afraid to cancel
Documentation is a product of all phases
Models of System Development Life Cycle
A SDLC defines the phases and tasks that are essential to systems development regardless of the size or scope of the impending system. While there are many versions or models of the SDLC, they differ only in terminology and are more often alike than dissimilar. In its simplest form, the SDLC consists of five phases: planning, analysis, design, implementation, and support. Following are examples of three different models, and have been included to further highlight the similarity between the phases and underlying principles.
The Waterfall Model
This model is sometimes known as the classic SDLC. It incorporates seven phases and depicts a method that is linear and sequential. The graphic representation of the phases in this model resembles the downward flow of a waterfall. Once a phase of development is completed, the development proceeds to the next phase. The Waterfall Model also allows the developer to return to previous phases for systematic reviews and to check procedures where necessary. Phases of this model are:
Planning
Analysis
Design
Construction
Implementation
Post Implementation Review
Maintenance
The Spiral Model
The spiral model incorporates the first five phases of the waterfall model listed above and is graphically illustrated as a continuing spiral, beginning from the centre and coiling around as the system grows. One could argue that the spiral model is actually a series of short waterfall cycles, each producing an early prototype representing a part of the entire project. This model emphasizes the need to go back and reiterate earlier stages a number of times as the project progresses. The spiral approach helps demonstrate a proof of concept early in the cycle, and resources can be held constant as the system size grows.
Rapid Application Development
In the rapid application development (sometimes called rapid prototyping) model, initial emphasis is on creating a prototype that looks and acts like the desired product in order to test its usefulness. The prototype is an essential part of the requirements determination phase, and may be created using tools different from those used for the final product. Once the prototype is approved, it is discarded and the “real” software is written. The four phases of this model are:
Requirements Planning
User Design
Construction
Cutover
Phases of System Development Life Cycle
All phases of the SDLC, regardless of the model, consist of a number of tasks that need to be undertaken in order to complete the life cycle. It is important to note here that while the phases are sequential in nature, overlapping and iteration of phases (and tasks) can occur. Using the waterfall model, the following table identifies phase tasks, their aims and their outcomes. Figure 1 illustrates how phases might overlap and has been provided to give a broad impression only. The actual overlap will depend on the scope of the system to be implemented and will vary considerably between projects.
Tasks
Key Stakeholders
Outcomes
Planning Phase. Beginning phase of the SDLC. Usually generated by a request from users and/or management to improve a current system or process
Survey project scope – Determine problem – Identify users
Survey project feasibility – Assess cost of new system
System analyst gathers information from management and users.
System