Mb0047

Q1. Explain DFD & Data Dictionary? Explain in detail how the information requirement is determined for an organization?
Ans: Data Flow Diagrams(DFD):
Data flow diagrams represent the logical flow of data within the system. DFD uses few symbols like circles and rectangles connected by arrows to represent data flows. DFD can easily illustrate relationships among data, flows, and external entities stores. DFD can also be drawn in increasing levels of detail, starting with a summary high level view and proceeding to more detailed lower level views..
The open-ended boxes represent data stores, sometimes called files or databases. These data stores correspond to all instances of a single entity in a data model. Arrow represents data flows, inputs and outputs to end from the processes. A number of guideline should be used in 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
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 that has already been used in an application. The difficulty to determine a correct and complete set of information is on account of the factors given below:
 The capability constraint of the human being as an information processor, a problem solver and a decision-maker.
 The nature and the variety of information in precise terms.
 Reluctance of decision-makers to spell out the information for the political and the behavioral reasons.
 The ability of the decision-makers to specify the information. In spite of these difficulties, methods are evolved based on the uncertainty scale, starting from the low to the high level of uncertainty.
There are four methods of determining the information requirements. They are:
 Asking or