Explain data flow diagram (DFD) & Data Dictionary? Explain in detail how the information requirement is determined for an organization?

Explain data flow diagram (DFD) & Data Dictionary? Explain in detail how the information requirement is determined for an organization?

Answer:
A data flow diagram (DFD) is a graphical representation of the flow of data through an information system, modelling its process aspects.
·         Often they are a preliminary step used to create an overview of the system.
·         DFDs can also be used for the visualization of data processing.
·         It represents the logical flow of data within the system.
·         DFD do not explain how the processes convert the input data into output.
·         They do not explain how the processing takes place.

• DFD uses few symbols like circles and rectangles connected by arrows to represent data flows.

• DFD can easily “this site”illustrate relationships among data, flows, external entities and stores.

• DFD can also be drawn in increasing levels of detail, starting with a summary high level view and proceeding o more detailed lower level views.

A number of guidelines should be used in constructing DFD.

• Choose meaningful names for the symbols on the diagram.
• Number the processes consistently. The numbers do not imply the sequence.
• Avoid over complex DFD.
• Make sure the diagrams are balanced.

Data Dictionary

Data Dictionary is a centralized repository of information about data such as meaning, relationships to other data, origin, usage, and format. Metadata is a data about data. So Data dictionary can also be called as metadata repository.

• The data dictionary is used to create and store definitions of data, location, format for storage and other characteristics.
• The data dictionary can be used to retrieve the definition of data.
• The data dictionary also stores some of the description of data structures, such as entities, attributes and relationships.

A schedule is made for the development of the system. While preparing the schedule due consideration is given to the importance of the system in the overall information requirement. Due regard is also given to logical system development. For example, it is necessary to develop the accounting system first and then the analysis.

Further, unless the systems are fully developed their integration is not possible. This development schedule is to be weighed against the time scale for achieving certain information requirement linked to a business plan. If these are not fully met, it is necessary to revise the time schedule and also the development schedule, whenever necessary.

The system development schedule is linked with the information requirements which in turn, are linked with the goals and objectives of the business. The selection of the architecture, the approach to the information system development and the choice of hardware and software are the strategic decisions in the design and development of the MIS in the organisation. 

 

The organisations which do not care to take proper decisions in these areas suffer from over-investment, under-utilisation and are not able to meet the critical information requirements.

Giving due regard to the technical and operational feasibility, the economics of investment is worked out. Then the plan of procurement is made after selecting the hardware and software. One can take the phased approach of investment starting from the lower configuration of hardware going over to higher as development takes place. The process is to match the technical requirements of the organisation over certain period of time.