With reference to assignments 8 and 9, what characteristics does an analyst(you) examine when evaluating DFD quality?
Before discussing the important characteristics a data flow diagram (DFD) must have, let us first understand the concept of the diagram. As the name suggests, data flow diagram is a description of the data with respect to the processes performed in a system. It shows the permanent storage of such data and its transformation into the system.
Data flow analysis tracks the flow of data through business processes and determines how organization objectives are met. It studies the use of data in each activity and documents the findings in data flow diagrams, graphically showing the relation between processes and data.
There are two types of data flow diagrams and one of these diagrams is physical data flow diagram, let us discuss physical dfd.
Physical DFD
Using PDFD is desirable for analysts for the following reasons:
1. It is easier to describe the interaction between physical components than to understand the policies used to manage the application. Identifying people, what they do, which documents and forms trigger which activities and what equipment is used in the processing. The movement of people, documents and information between departments and locations is also identified.
2. Physical data flow diagrams are useful for communicating with users. Users relate easily to people, locations and documents as they work with these each day. Users may consider logical DFDs abstract as they do not contain these familiar components, however, with physical DFDs users can quickly identify incorrect or missing steps.
3. Physical DFDs provide a way to validate or verify the user's current view of the system with the way it is actually operating. If there are differences, they will be noted and discussed. It is not unusual to find that what a users thinks is happening differs in an important way from what actually occurs.
Evaluating Data Flow Diagrams for Correctness
A quality DFD should consider correctness as its primary characteristic. Correct DFD indicates that the analyst understand the data flows in the business processes of its clients. Understanding between the clients and the developer is the key factor in producing a good system. And developing a good system starts from its developing particularly in creating diagrams such as the DFD.
It is essential to evaluate all DFDs carefully to determine if they are correct. Errors, omissions and inconsistencies can occur for several reasons, including mistakes in drawing the diagrams. But the presence of what appears to be an error may in fact point out a deficiency in the system or a situation in which users are not aware of how certain processes operate.
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