Software Development methodologies

Software Development methodologies

1. Prototyping

   • 2 type of main prototyping
     • Evolutionary
       • An initial prototype is developed and evaluated by the end users. Using the feedback from the 2nd prototype is developed and then evaluated.
         • Process continues with each prototype and evaluation making the system closer to what the end user needs.
     • Throw - away
       • When a working model of a various parts of the system is developed is developed after a short investigation
       • developed and evaluated by the end-user but doesn't used in the final solution.
       • enables the end users to give, and receive quick feedback so that any improvements can be done early.
       • early changes in the development = cost effective because there is nothing to redo. if the project is changed early in the development after considerable work has been done then small changed could require large efforts to implement since software systems have many dependencies.
   • stresses the early delivery of an incomplete but working system that can be changed following feedback fro the client
   • main purpose is to allow the end user to evaluate the proposals of the design of the software by trying them out
   • First attempt at a design, which is then extended and enhanced throughout the interactions
   • Can take place at different stages of the development life cycle, but the methodologies must be planned to get the maximum feedback from the end user.
   • stimulates only a few aspects of the software system and may be completely different from the final solution
   • Can be used to verify that what the designer has imagined is what the end user requires.
   • Can also be used by the end users to describe requirements that the designer may have not considered, so controlling the prototype can be a key factor in the relationship between the designer and the end useres.
   • designs can be demonstrated, designs can be tried out and problems with possible solutions can be investigated.
   • Advantages and disadvantages
     • Reduce time and costs
       • prototyping can improve the quality and specifications provided to developers.
       • changes costs increase more to implement so early clarification can result in fast development and smaller costs.
     • Excessive development time of the prototype
       • talking too long to develop a prototype which can lead to an increase of cost of the resources needed
       • not appropriate to use this methodology is the user requirements are already established or the ystsem is a standard pe used by the organisation
     • Confusion between the prototype and the finished system.
       • Can lead the end users to expect the prototype to match accurately the final system; they think that a prototype is intended to be thrown away but it is actually a final system that just needs to be finished
       • users can become attach to some feature that were included in a prototype for user evaluation and then removed from the final system,
     • Improved and increased improvements
       • involvement of users can provide better and more complete feedback and specifications
       • increase in user involvement can result in better and more appropriate final product that will satisfy the end users' needs in terms of look, feel and performance
       • the designer can obtain feedback from the end users early in the project to ensure that it meets the requirements and the deadlines proposed can be met.

2. Rapid Application Development (RAD)

   • typical duration of a RAD system is less than six months. generally considered to be the longest period over which user requirements will stay static.
   • 2 main features
     • 1st is JOINT APPLICATION DEVELOPMENT JAD workshops. These aims to develop a set of requirements that should not change before the system is implemented.
     • 2nd feature TIMEBOXING. requirements are defined in chunks each if which is considered using JAD
       • each chunk has a deadline which must not exceed.
       • at the start if each timebox - the objectives are defined and at the end of timebox these are evaluated. If requirements are not successfully completed then may add another timebox or dropped. If timeboxes cant be completed, then the overall may need to be reviewed.
   • a software development methodology based on a system life cycle that is iterative and evolutionary
   • 2 main benefits - short duration and increased opportunities for user involvement. this will ensure that no changes were made to the end-users requirements towards the end of the development process.
   • during the process tools can be used like GUI (Graphical User Interface) that can be seen by and evaluated by the end user. use of these tools is to visualise the GUI and provide helpful feedback to the development team before the system is implemented
   • the involvement should ensure that the system meets all the requirements once is fully developed and implemented.
   • RAD attempt overall control over the development process, but also provides continual feedback on the progress of ta project. means if any slippage int he defined time schedule, then plans can be adjusted.
   • RAD is also helpful to the end users of the system being developed. They are party to evaluations which means they are continually involved.
   • Advantages and Disadvantages
     • the end user is involved in all stages with the system being implemented within six months
     • End users are involved are involved in the evaluation so this should ensure that requirements are being met.
     • End users do not have to define all the requirements of the system at the beginning of the process
     • the solution developed using RAD may meet the requirements but the functionality may not be acceptable
     • the project manager, who is supervise the development of the system, will need to keep very tight control over the whole development process and the team, if the system is to be developed within the six months deadline required by RAD.