Data Flow Diagrams Explained
A data flow diagram is a graphical way of depicting a sequence of data flowing through a network or a process. The DFD provides information on the inputs and outputs of every entity involved in the process and the entire process itself. A data-flow diagram has no subject-specific direction, instead it is a globally consistent model. However, it can be visualized using only a few graphics packages like Microsoft Office PowerPoint. A data flow diagram can also be created manually by following some simple steps. Data visualization in Processing is based on a data model that can be easily created in-house.
A data-flow diagram visualizes the data flow in a logical way. This can be seen as a tree diagram where the different nodes represent data, while the roots are logical functions that define the relationships among them. Each of the logical processes corresponds to one or more nodes. A logical function can be one of the following:
The use of a data-flow diagram in Processing is based on the context theory. Context diagrams are very similar to the hierarchy diagrams used in various areas of research such as anthropology, sociology, and computer science. The difference lies in the fact that context diagrams depict a particular situation (the data-flow) while a hierarchy depicts a logical order of related objects. Also, both context diagrams and hierarchy diagrams can be created automatically by using the same graphic programs such as Microsoft Office.
When you create a data-flow diagram, you need to identify all the processes involved. You need to keep in mind that there might be multiple processes involved and the relationships among them should be identified clearly. For instance, in the case of a manufacturing plant, the positions of all the machines are clearly indicated. In addition, the symbols used for labeling each machine are different. The data flow from the input devices to the output devices, from input to the machines and from machine to output are also clearly indicated. The diagrams can be viewed in either a side-view or top-down views.
The format of the data-flow diagram is determined by the data it represents. You can find rectangular, square, and other shapes depending on what the diagram represents. Different graphical user interface systems also provide alternative shapes for the rectangles. However, it should be noted that if the output devices do not have the same shape, then you cannot simply copy the rectangles into the corresponding places on the other devices.
The common data flow patterns associated with many industrial processes include:
In addition, you can also find graphical diagrams that depict the main difference in each piece of equipment. When an entire system has to be analyzed, it is much easier to make a single graphical diagram that shows all the processes involved. This makes it easier to determine the flow of materials, components, and labor in the entire system. It allows one to easily visualize the entire process in the event that more than one person is needed to handle different tasks. The key point is that these diagrams are created to make it easier for a manager or engineer to understand the data flow and identify the problems.
The main difference between these two diagrams is not their format but how they are visualized. A data-flow diagram lays out the data flows that go through an entire production process. It shows each input as well as each output. An external entity view is usually seen when you need to identify what the external entities are. The main difference is that the external entity view gives details about the physical actions of the external entities take, whereas the data flow in a data-flow diagram, the flow is shown on an external entity.
