The systems life cycle (sometimes called the ‘project life cycle’) can be confusing! This is because every author has his or her own idea of exactly what it means, what jobs should be done in each stage and what documents should be produced. On top of that, people will combine or split certain stages in the life cycle and then use different words to describe the same thing, or the same words to describe different things!! There is no getting away from this problem but you do need to tackle it head on. You must read around the subject. Read four or five different descriptions of the systems life cycle and then make your own mind up to truly get an idea of it. The phrase ‘systems life cycle’ simply describes the steps that are taken in a project, from the time that the project is started to when it is finished. When any computer-related project is initiated, a number of distinct steps, or stages, can be identified in the life of the project. Each of these stages will involve people doing jobs and producing 'things', for example, a design document, a test plan or a piece of program code. Each of these things takes the project a little further towards completion. Things that have to be produced for each stage are known as ‘deliverables’, for example, a report.

The idea behind the systems life cycle is that the deliverables associated with each stage in the project must be produced and checked off by the Project Manager before the next stage can begin. A stage cannot be started until the previous stage is finished. This stops a project getting ahead of itself. For example, it will stop someone trying to start the stage called 'implementation' (the stage where you actually make the project using a database application or code) before all of the design documentation has been completed. You may have had some experience of this scenario yourselves with coursework - you don't want to do the paperwork or a detailed design, you just want to get on and do the project! This, however, is the road to potential disaster! For example:

  • How can a project be designed if it is not clear what the problem is?
  • How can a project be built if it is not designed?
  • How can it be installed if it is not properly tested?
  • What happens if a key project member leaves - how can someone new pick up where they left off if half of the paperwork is missing or incomplete?
  • How can a Project Manager accurately manage a project if they can't clearly see that deliverables are being completed on time and within the budget?
  • How can someone make changes to the product in the future if the documentation is incomplete?

The list of potential problems goes on and on. A systems life cycle gives a project a structure and therefore allows a Project Manager to manage the project rather than reacting to things when they go wrong! We can summarise the systems life cycle with the following diagram (called the 'waterfall model'):


Notice with this model that there is nothing stopping a stage feeding back into an earlier stage, so that the project can constantly loop around until it is perfect!

An alternative approach - Rapid Application Development (RAD) - the Spiral Model

We will briefly mention here the RAD approach to project development as an alternative to the traditional systems life cycle approach because it has become very important recently with the rise of something called 'Object Oriented Programming'.

The traditional waterfall approach has some drawbacks. For example, it can take a while for customers to actually see the final product. Another concern is that software produced using this approach in theory is easy to change but in practice is difficult. The RAD approach is different to the classic systems life cycle. It involves designing and building a series of prototypes. After each one is built, the user is involved. They are asked to try out and comment on features and test some of the functions. Their comments are then fed back into the next design and prototype and a better one is produced. This process is repeated until the product is finished. After each round, the product spirals closer to the desired product. This process is sometimes called the Spiral Model as a result. The product is in effect developed a little bit at a time but constantly involves the customer throughout the development process. It is very common to combine the classic waterfall model with a prototyping approach; the waterfall model is followed, but the design and implementation stages involve the user commenting on a series of prototypes.

Business | Systems

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