System Development Life Cycle

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Introduction

Software systems development is, from a historical perspective, a very young profession. The first official programmer is probably Grace Hopper, working for the Navy in the mid-1940s. More realistically, commercial applications development did not really take off until the early 1960s. These initial efforts are marked by a craftsman-like approach based on what intuitively felt right. Unfortunately, too many programmers had poor intuition.

By the late 1960s it had become apparent that a more disciplined approach was required. The software engineering techniques started coming into being. This finally brings us to the SDLC. What evolved from these early activities in improving rigor is an understanding of the scope and complexity of the total development process. It became clear that the process of creating systems required a system to do systems. This is the SDLC. It is the system used to build and maintain software systems.

The System Development Life Cycle is the process of developing information systems through investigation, analysis, design, implementation, and maintenance. 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.

SDLC Objectives

When we plan to develop, acquire or revise a system we must be absolutely clear on the objectives of that system. The objectives must be stated in terms of the expected benefits that the business expects from investing in that system. The objectives define the expected return on investment.

An SDLC has three primary business objectives:
- Ensure the delivery of high quality systems;
- Provide strong management controls;
- Maximize productivity.

In other words, the SDLC should ensure that we can produce more function, with higher quality, in less time, with less resources and in a predictable manner.

1. Ensure High Quality

Judging the quality of a wine or a meal is a subjective process. The results of the evaluation reflect the tastes and opinions of the taster. But we need a more rigorous, objective approach to evaluating the quality of systems. Therefore, before we can ensure that a system has high quality, we must know what quality is in a business context. The primary definition of quality in a business context is the return on investment (ROI) achieved by the system. The business could have taken the money spent on developing and running the system and spent it on advertising, product development, staff raises or many other things. However, someone made a decision that if that money was spent on the system it would provide the best return or at least a return justifying spending the money on it.

This ROI can be the result of such things as: operational cost savings or cost avoidance; improved product flexibility resulting in a larger market share; and/or improved decision support for strategic, tactical and operational planning. In each case the ROI should be expressed quantitatively, not qualitatively. Qualitative objectives are almost always poorly defined reflections of incompletely analyzed quantitative benefits. The SDLC must ensure that these objectives are well defined for each project and used as the primary measure of success for the project and system. The business objectives provide the contextual definition of quality. There is also an intrinsic definition of quality. This definition of quality centers on the characteristics of the system itself: is it zero defect, is it well-structured, it is well-documented, is it functionally robust, etc. The characteristics are obviously directly linked to the system's ability to provide the best possible ROI. Therefore, the SDLC must ensure that these qualities are built into the system. However, how far you go in achieving intrinsic quality is tempered by the need to keep...
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