SDLC, the Systems Development Life Cycle relates to models or methodologies that people use to develop systems, generally computer systems. Note: the acronym is sometimes thought of to represent Software Development Life Cycle and sometimes the process/model is simply referred to as the SLC. Computer systems have become more complex and usually (especially with the advent of Service-Oriented Architecture) link multiple traditional systems often supplied by different software vendors.

To manage this, a number of system development life cycle (SDLC) models have been created: waterfall, fountain, spiral, build and fix, rapid prototyping, incremental, and synchronize and stabilize.

SDLC adheres to important phases that are essential for developers, such as planning, analysis, design, and implementation, and are better explain in the section below. The oldest model, that was originally regarded as “the SDLC” is the waterfall model: a sequence of stages in which the output of each stage becomes the input for the next. These stages generally follow the same basic steps but many different waterfall methodologies give the steps different names and the number of steps seems to vary between 4 and 7.

There is not a definitive correct model, but the steps can be characterized and divided as follows:

• Project planning, feasibility study, Initiation: To generate a high-level view of the intended project and determine the goals of the project. The feasibility study is sometimes used to present the project to upper management in an attempt to gain funding. Projects are typically evaluated in three areas of feasibility: economical, operational, and technical. Furthermore, it is also used as a reference to keep the project on track and to evaluate the progress of the MIS team (Post & Anderson, 2006)

• Requirements gathering and Systems Analysis: The goal of systems analysis is to find out where the problem is in attempt to fix the system. This step involves breaking down the system in different pieces and drawing diagrams to analyze the situation. Analyses project goals, breaking down functions that need to be created, and attempts to engage users so that definite requirements can be defined.

• Systems design: Functions and operations are described in detail, including screen layouts, business rules, process diagrams and other documentation. The output of this stage will be to describe the new system as a collection of modules or subsystems.

• Build: Modular and subsystem programming code will be accomplished during this stage. This stage is intermingled with the next in that individual modules will need testing before integration to the main project.

• Testing: The code is tested at various levels. Unit, system and user acceptance testing are often performed. This is a very grey area as many different opinions exist as to what the stages of testing are and how much if any iteration occurs. Iteration is not generally part of the Waterfall model, but usually some occurs at this stage.

• Installation, Implementation or Deployment: The final stage of a project or the initial development, where the software is put into production and is used by the actual business.

• Maintenance, Business as Usual: The life of the system which includes changes and enhancements before the decommissioning or sunset of the system. Maintaining the system is a very important aspect of SDLC. As key personnel change position in the organization, new changes will be implemented, which will require system updates.

Baselines in the SDLC

Baselines are an important part of the SDLC. These baselines are established after four of the 5 phases of the SDLC and are critical to the iterative nature of the model (Blanchard & Fabrycky, 2006, p.31). Each baseline is considered as a milestone in the SDLC.

Functional Baseline: Is established after the conceptual design phase.

Allocated Baseline: Is established after the preliminary design phase.

Product Baseline: Is established after the detail design and development phase.

Updated Product Baseline: Is established after the production construction phase.

Very few people in the modern computing world would use a strict waterfall model for their SDLC as many modern methodologies have superseded this thinking. Some will argue that the SDLC no longer applies to models like Agile computing, but it is still a term widely in use in Technology circles.

An alternative to the SDLC is Rapid Application Development; which combines prototyping, Joint Application Development and implementation of CASE tools. The advantages of RAD are speed, reduced development cost, active user involvement in development process.

It should not be assumed that just because the waterfall model is the oldest original SDLC model that it is the most efficient system. At one time the model was beneficial mostly to the world of automating activities that were assigned to clerks and accountants. However, the world of technological evolution is demanding that systems have a greater functionality that would assist help desk technicians/administrators or information technology specialist/analyst.

Alternatives to SDLC

• Software Prototyping
• Joint Applications Design (JAD)
• Rapid Application Development (RAD)
• Extreme Programming (XP); extension of earlier work in Prototyping and RAD.
• Open Source Development
• End-user development
• Object Oriented Programming