The System Lifecycle

Definition of the problem
1. The feasibility of the proposed system is considered.
2. This stage is also known as "the feasibility stage"
3. An initial look at the existing system to see how it can be improved or meet the needs of the end user
4. A feasibility report is produced at the end of this stage
5. Main Process Constraints
  1. Time
  2. Budget
  3. Hardware Choice
  4. Software Choice
6. Important Questions that should be answered in this stage
  1. Can the need for a new system be justified?
  2. Is it technically feasible and economically desirable to the end users?
  3. Can the solution be designed and implemented within the given constraints of timescale allocated and budget?
  4. Will the solution have a positive impact on the end users and will the new system bring benefits
  5. Will the solution fulfil all the needs and requirements of the end users
Design
1. The design stage follows a set of objectives (the requirement specification) that have been defined in the investigation and analysis stage
2. The methods of data capture that are going to be used have to be considered to make sure that they are compatible with the new system
3. The preparation, input, process, output and storage of the data must also be considered
  1. This also covers such activities as the design of the user interface and the screen layout
4. The structure of the data must be defined together with the processing and the validation routines that will be used
  1. Development of any user feedback requirements (error messages) should be linked with this
5. The design of the queries and reports that have to be identified as requirements during the investigation stage needs to be considered as well
6. The main output from this stage is the design specification
Doumentation
1. The documentation that gets passed to the end user includes
  1. Detailed program specifications
  2. Recovery procedures
  3. Operating procedures
  4. User manuals
  5. Test plans, data and logs
  6. Security details
  7. Version details
  8. Technical details for associated hardware
Investigation and Analysis
1. This stage uses the feasibility report as its main input
2. The full nature of the problem is investigated in this stage
3. Methods of investigating the current system
  1. Questionnaires
  2. Interviews
  3. Meetings
  4. Document Analysis
  5. Observations
4. The results of the investigation have to be fully analysed to gain a full understanding of the current system
  1. If the investigation is incomplete, the new system may not cover all the issues with the current system
    1. Therefore, the new system may not benefit the organisation
5. The user requirements have to be defined during this stage
  1. The requirements are agreed with the client and will form the basis for the rest of the system lifecycle
    1. The agreed needs/ requirements are the output of this stage (the requirement specification)
6. The requirement specification has to be constantly referred to to make sure that the new system meets all of the criteria of this
Implementation
1. This stage is also known as the development stage
2. This stage uses the design specification as its main input
3. During this stage, programmers will create the code required for the software solution.
  1. This includes the development of the user interfaces and outputs, which were designed in the design stage
  2. Any macros, processing and queries that are required by the client must be developed as well
4. The main output of this stage will be working software code that is ready to be tested
Testing
1. Two main functions of this stage
  1. If there are any bugs or errors in the code
  2. If the system correctly meets the defined user requirements
2. A well-defined and comprehensive test plan must be produced
  1. The test plan must be followed and results must be documented
3. This stage can be vey expensive and time consuming but if it carried out correctly and throughly there will be fewer bugs and issues with the new system
Evaluation and Maintenance
1. This is the final stage of the system lifecycle.
  1. This stage concludes the whole cycle and a report is produced to summarise each stage of the project and all finds, problems encountered.
Installation
1. Parallel
  1. This type of installation is when the new system is run along the existing system. This allows any persistent bugs with the new system to be corrected without affecting the day to day running of the company. Once all problems have been resolved, the existing system will be withdrawn from operation and the new system will run on its own
    1. An example of this type of installation is self service checkouts in supermarkets
2. Phased
  1. This type of installation is when a new system is introduced into the company is stages ("phases"). This is done by running the new system in certain departments or areas
    1. An example of this is self service checkouts in supermarkets. This is because they were introduced to a few shops to start with to see how consumers reacted to the change and then converting the rest of the stores to the new system
      1. This is still an ongoing process for some supermarkets because not all of their stores are running the new system. In this case, self service checkout system
3. Pilot
  1. This method of installation is done by introducing the system to one department or store to see how it works
    1. There is less of a risk involved in this type of installation because if the new system is unsuccessful, it can be withdrawn easily with little disruption
4. Direct
  1. This type of installation is done by introducing the new system to the company in one hit. The existing system is removed and the new system is left to run on its own.
    1. This is a risky method of installation because the new system may not work due to undiscovered bugs or because users may not be able to adapt fast enough to use the new system

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The System Lifecycle

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	Created by harry.spong over 10 years ago