System Development Life Cycle (SDLC): The Systems Development Life Cycle (SDLC) is a conceptual model used in project management that describes the stages involved in an information system development project, from an initial feasibility study through maintenance of the completed application.
The SDLC is used by a systems analyst to develop an information system, including requirements, validation, training, and user ownership through investigation, analysis, design, implementation, and maintenance. SDLC is also known as information systems development or application development. An SDLC should result in a high quality system that meets or exceeds customer expectations, within time and cost estimates, works effectively and efficiently in the current and planned information technology infrastructure, and is cheap to maintain and cost-effective to enhance. SDLC is a systematic approach to problem solving and is composed of several phases, each comprising multiple steps.
a) Definition: Systems Development Life Cycle (SDLC) or sometimes just (SLC) is defined by the U.S. Department of Justice (DoJ) as a software development process, although it is also a distinct process independent of software or other Information Technology considerations.
b) SDLC Methodologies: Various SDLC methodologies have been developed to guide the processes involved, including the following:
i) Waterfall model (which was the original SDLC method);
ii) Rapid Application Development (RAD);
iii) Joint Application Development (JAD);
iv) The fountain model;
v) The spiral model;
vi) Build and fix;
Frequently, several models are combined into some sort of hybrid methodology.
Documentation is crucial regardless of the type of model chosen or devised for any application, and is usually done in parallel with the development process. Some methods work better for specific types of projects, but in the final analysis, the most important factor for the success of a project may be how closely the particular plan was followed.
c) The Systems Life Cycle (UK Version): The SDLC is referred to as the Systems Life Cycle (SLC) in the United Kingdom, whereby the following names are used for each stage:
i) Terms of Reference: The management will decide what capabilities and objectives they wish in the new system to incorporate;
ii) Feasibility Study: Asks whether the managements' concept of their desired new system is actually an achievable, realistic goal, in-terms of money, time and end result difference to the original system. Often, it may be decided to simply update an existing system, rather than to completely replace one;
iii) Fact Finding and Recording: How is the current system used? Often questionnaires are used here, but also just monitoring (watching) the staff to see how they work is better, as people will often be reluctant to be entirely honest through embarrassment about the parts of the existing system they have trouble with and find difficult if merely asked.
iv) Analysis: Free from any cost or unrealistic constraints, this stage lets minds run wild as “wonder systems” can be thought-up, though all must incorporate everything asked for by the management in the terms of reference section.
v) Design: Designers will produce one or more “models” of what they see a system eventually look like, with ideas from the analysis section either used or discarded. A document will be produced with a description of the system, but nothing is specific - they might say “touchscreen” or “GUI operating system”, but not mention any specific brands.
vi) System Specification: Having generically decided on which software packages to use and hardware to incorporate, you now have to be very specific, choosing exact models, brands and suppliers for each software application and hardware device.
vii) Implementation and Review: Set-up and install the new system (including writing any custom (bespoke) code required}, train staff to use it and then monitor how it operates for initial problems, and then regularly maintain thereafter. During this stage, any old system that was in-use will usually be discarded once the new one has proved it is reliable and as usable.