No matter how skilled you are in using a computer, it will not solve problems for you. Information systems are used as tools to aid problem solving; they do not develop solutions themselves. When we encounter a problem, we embark on some strategy to solve that problem whether we are aware of it or not.
The same goes for the development of any successful information system. It requires careful planning to ensure that it meets the needs of the users and assists the organisation in meeting its goals.
The two most common approaches are the Top Down approach and the Bottom Up approach. The basic difference is the starting point of each method.
Top down (analytical)
Example: Consider a system, the overall goal of which is to provide a means of tracking the financial performance of a company. In order to achieve this goal, the system must be able to track two things: income generated and money spent. These two areas form the next level of the system, and they can be broken down into further subsets, which in turn can be broken down into smaller subsets or tasks.
Example: The top-down technique may be applied to a school student record system. The major function of the system will be to store and maintain accurate student information. The output required could be class lists; students sorted by details such as name and address; students selected by key information such as age. The main function could be broken down into such tasks as adding, deleting, editing and searching for selected information and sorting student records. Each task will require a set of inputs and procedures to complete the task.
This approach is also referred to as a modular approach, and is closely related to the use of data flow diagrams. The major benefit of this approach is that the tasks are broken down into smaller manageable ones, and each can be developed in a manner that allows the system to quickly take shape. Further, the system can easily be broken up into related tasks, and the structure defined so all interdependencies are clearly identified and understood. Because of the significant amount of analysis that this method relies upon, it is often referred to as an analytical approach.
In the top-down approach, the functions are broken down into smaller tasks, whereas the bottom-up approach starts with the lowest level and builds up a solution. We start by considering the data input and then use this to identify the possible data outputs and the processes required to produce these outputs.
Example: We may wish to analyse the results of a survey. We can easily identify the data input on the survey forms. From the input data, we can identify many possible types of output, for instance bar graphs, or tables. We could also correlate results such as comparing incomes with places of residence on census forms. Once we identify the outputs desired, we can determine the processes needed.
Another common method used is the iterative technique. This technique requires the user to produce a quick solution that may be imperfect, and then refine this solution until it meets all the requirements. It produces a number of intermediate solutions, each one progressively closer to a final solution. The aim of this technique is not to produce a perfect solution, but to produce a solution that meets all the constraints.
Example: This technique can be seen operating in most schools when a timetable is developed at the start of a new year. The timetabler will begin with an immense amount of raw data and many constraints that the solution must conform to. The timetabler will first create an initial solution that includes as much of the raw data and constraints as possible. This intermediate solution becomes the input to the next stage and is progressively refined to include more data and constraints until a final working solution is obtained.