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The Systems Development Life Cycle (also sometimes known as the Software Development Life Cycle) is a framework which is employed when either creating or modifying information systems. It can be utilised across a wide spectrum of subjects and methods within the fields of software engineering and systems engineering. The cycle is both solid enough to provide a firm underpinning no matter what the activity being undertaken, whilst also still being sufficiently flexible to be utilised whatever the dynamics of the individual situation, with defined steps which can, if required, be combined or overlapped, should this be needed.

In the simplest terms, the cycle moves forward through the following stages:

Analysis  Design Implementation Testing Evaluation

This is only a brief and simplified explanation, and a more in depth description of each of the stages will be laid out subsequently. The point of an SDLC is that it forms a firm foundation, on top of which an effective system can be constructed. An SDLC will, in some ways, act as a safety net and constraint upon the development, ensuring that it meets the requirements of the client and doesn’t run over in terms of either budget or timescale. At the start of the process, the idea of developing an information or software system can seem incredibly daunting, complex and difficult, with many different factors, both internal and external, to be taken into account and seamlessly blended. A process which breaks this down into incremental steps, whilst still allowing sufficient flexibility to meet unpredictable events and circumstances, is one which can be taken from one situation to another whilst meeting all and any requirements.

There are various different models of SDLC available, differing in flexibility and complexity, with names such as fountain, rapid prototyping, spiral and build and fix. By far the most firmly established, well know and easiest to use is the waterfall model. In this model, the output of each stage forms the input of the next stage, making it instinctively simple to work with and understand. As stated earlier, the core of the system lies in breaking the process down into individual steps, based roughly around the areas of analysis, design, planning and implementation. Although the number and nature of these steps can vary from project to project, there is a basic pattern to be followed from initiation through to creation and modification. In simple terms, the SDLC can be broken down as follows:

System Development Life Cycle (SDLC) Life - Cycle Phases

 
 
 
 
 
 
 
 
 

Initiation

A need, requirement or opportunity is identified, leading to the creation of a proposal for a system which will slot into this gap.

System Concept Development

Crystallises the themes and content identified in the previous stage. Lays out the exact scope and defined boundaries of the project, and will often involve the drafting of documents relating to the Systems Boundary, Cost Benefit Analysis, Risk Management and an overarching Feasibility Study.

Planning

This stage of the cycle involves drawing up any planning documents needed to pull the project management together. It’s here that any resources required for an effective solution will be identified and sourced.

Analysis of Requirements

This stage looks at the needs of the user of the system and creates a document based around these requirements.

Design

This stage of the cycle takes the requirements identified in the previous step and uses them as the basis of a detailed Systems Design Document. This is meant to look in depth at the function which the system is intended to perform, and outline how to ensure delivery.

Development

This involves the actual solid work entailed in turning a design into an actual system. The system environment needs to be installed, databases created and tested, the programmes needed have to be coded, compiled and refined.

Testing

Having completed the previous step, the system now has to be put through its’ paces and tested with reference to the document created at the Analysis of Requirements stage. A report based on this test should be produced.

Implementation

At this stage the work done so far should lead naturally to the system being implemented in a real world environment. Any problems identified in the phase which came immediately before this should now be resolved.

Operation / Maintenance

This stage consists of compiling the steps and processes necessary to maintain and operate the system on an ongoing basis. This requires a Review of the system in situ, looking at how it performs.

Initiation

A need, requirement or opportunity is identified, leading to the creation of a proposal for a system which will slot into this gap.

Example: Any business wishing to establish a strong online presence via a website would be wise to use an SDLC when setting up this website, or employ the services of an agency which does so. The days when a website was merely an online version of a brochure are long gone and ensuring that all facets of the site are integrated and work as smoothly as possible will require the secure and solid framework which an SDLC provides.

System Concept Development

Crystallises the themes and content identified in the previous stage. Lays out the exact scope and defined boundaries of the project, and will often involve the drafting of documents relating to the Systems Boundary, Cost Benefit Analysis, Risk Management and an overarching Feasibility Study.

Example: At this stage in the process, the people building online pharmacy kind of site which would have focused upon what the aims of the site were. In this case the clearest requirements would have been for simple, clean displays, fast navigation and a secure and speedy payment method. On top of these basics, given the nature of the goods being sold, clear access to information which is well presented should be built in from the very start.

Planning

This stage of the cycle involves drawing up any planning documents needed to pull the project management together. Itís here that any resources required for an effective solution will be identified and sourced.

Example: Let's consider the example of a website which transforms digital photographs into framed canvas prints. The planning stage of this site would entail ensuring that the technical requirements needed to display the examples on the site in the best possible manner were in place, and that any resources required for this (i.e. specialist photography and image manipulation) had been sourced and priced.

Analysis of Requirements

This stage looks at the needs of the user of the system and creates a document based around these requirements.

Example: At this stage in the process the specifics of what the actual end user requires can be brought sharply into focus. Let's consider the example of online car hire portal website which is focused on moving the consumer through the process as quickly as possible, meaning that the requisite information (hire rates etc) is displayed at once and in the same place and is easily understood.

Design

This stage of the cycle takes the requirements identified in the previous step and uses them as the basis of a detailed Systems Design Document. This is meant to look in depth at the function which the system is intended to perform, and outline how to ensure delivery.

Example: By this stage in the process, the focus will be clearly on the finished site or system. Let's consider the online food ordering & delivering site for example, as well as being easy and quick to navigate, will need to be set up to invoke the atmosphere and ethos of an artisan food shop. Thus, the delivery wonít be merely about technical aspects, but also about the Ďfeelí of the site and the image it invokes.

Development

This involves the actual solid work entailed in turning a design into an actual system. The system environment needs to be installed, databases created and tested, the programmes needed have to be coded, compiled and refined.

Example:In all of the cases cited above, this is the stage on the cycle during which the mechanics of the site are actually put in place, and for which the information gathered thus far will prove absolutely priceless.

Testing

Having completed the previous step, the system now has to be put through its’ paces and tested with reference to the document created at the Analysis of Requirements stage. A report based on this test should be produced.

Example: The website for the electrical appliance store www.hispek.com is one which would have to be tested in terms of its’ raw functionality. Is everything displayed as it should be? Can items be accessed easily? Does the search function work properly? Is moving from finding an item to paying for it quick and simple?

Implementation

At this stage the work done so far should lead naturally to the system being implemented in a real world environment. Any problems identified in the phase which came immediately before this should now be resolved.

Example: For all of the examples listed above, and any other sites, software or systems, an SDLC, followed as a logical progression from step to step, should ensure that, by the time the Implementation stage is reached, all problems have been either addressed or identified.

Operation / Maintenance

This stage consists of compiling the steps and processes necessary to maintain and operate the system on an ongoing basis. This requires a Review of the system in situ, looking at how it performs.

After following these steps, the system itself will be up and running. It may then be decided to put together a document detailing the process and any observations to be made as the system is launched. The above is a description of the basic steps in the cycle, but, depending upon the size and complexity of any given project, individual steps may be combined or overlap.
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