The top down approach assumes and focuses on organizational goals, objectives and strategies. The logic here is that, above all, an information system needs to be responsive to and supportive of an organization’s basic reasons for being. Hence the organization’s goals should be the driving force behind development of all the computer systems.
Using top down approach, we begin by analyzing organizational objectives and goals and end by specifying application programs, and modules that need to be developed to support those ion’s goals. The various stages in top down approach are as follows:
(a) Analyze the objectives and goals of the organization to determine where it is going and what management wants to accomplish. The analysis may be stated in terms of profits, growth, expansion of product line or services, diversification, increased market share and so on. It is also determined what resources are available in terms of capital, equipments and raw materials.
(b) Identify the functions of the organization (for example, marketing production, research and development) and explain how they support the entire organisation.
(c) Based on the functions identified above, ascertain the major activities, decisions and functions of the managers at various levels of hierarchy. It should also be analysed what decision are made as well as what decision need to be made and when they should be made.
(d) What activities and decisions identified, we must now identify models that guide managerial decision processes and find out the information requirements for activities and decisions. An insight should be provided into what information is needed when it is needed and what form is most useful. These factors provide many of the design specifications for the application system.
(e) Prepare specific information processing in detail and modules within these programmes. We may also identify files and data base for applications.
The development of information system under this approach starts from the identification of life stream system. Life stream systems are those systems, which are essential for the day-to-day business activities. The examples of life stream systems include payroll, sales order, inventory control and purchasing etc. The development of information system, for each life stream system
starts after identifying their basic transactions, information file requirements and information processing programs.
After ascertaining the data/information requirements, files requirements and processing programs for each life stream systems the information system for each is developed. The next step is towards the integration of data kept in different data files of each information system. The data is integrated only after thoroughly examining various applications, files and records. The integrated data enhances the share-ability and evolability of the database. It also ensures that uniform data are being used by all programs. Integrated data also provides added capability for inquiry processing and adhoc requests for reports.
The next step under bottom up approach may be the addition of decision models and various planning models for supporting the planning activities involved in management control. Further, these models are integrated to evolve model base. The models in the model base facilities and support higher management activities. They are useful for analysing different factors, to understand difficult situations and to formulate alternative strategies and options to deal them.
A comparison of top down and bottom up approaches reveals the following points:
1. Top management takes the main initiative in formulating major objectives strategies and policies, for developing MIS under top-down approach. In the bottom up, approach it is the supervisory management who identifies the life stream systems for which MIS may be development.
2. Middle and supervise management levels have a little role in the development of system under top down approached. Under bottom up approach management refrains from guiding the development of system developed by supervisory level.
3. The information system development under top down approach is more consistent with the systems approach and is also viewed as a total system, which is fully integrated. The information system developed under bottom up approach is developed through an orderly process of transition, building upon transaction processing sub-system. This system may not be integrated.