Data Flow Diagram of Software Engineering (DFD Data Flow diworkflow)

 1. What is a data flow diagram?

A data flow chart is a graphical system model. It shows the data flow of the information system in a diagram-that is, what is the input and output data of the system, where the data comes from and eventually flows, and where the data is stored.

The basic graphic elements of a data flow chart are:

• Data Stream: It is composed of a set of fixed data, indicating the data flow. It is worth noting that the data flow diagram describes the data flow rather than the control flow. In addition to data flowing to or from data storage, you do not need to name the data flowing out. Each Data Stream must have a proper name to reflect the meaning of the data stream.
• Processing: Processing describes the transformation between the input data stream and the output data, that is, after which the input data stream is processed, it becomes the output data. Each processing task has a name and a number. The number indicates the layer and graph of the data flow graph in which the processing is located, and shows which processing is used to separate the data flow graph.
• Data storage: Data Storage refers to the data temporarily stored. Each data storage has a name.
• External entity: an external entity is a person or organization that exists outside the software system. It indicates the source of the data required or the geographic location of the data produced by the system.

Ii. Why do I draw a data flow chart?

Data Flow diagram, the software designer can analyze the information flow of the system from top to bottom, determine the part to be processed by the computer on the graph, transition to the database design, determine the access method based on the data flow, and determine a processing process.. During the test, the data flow diagram can help the programmer find the location where the error occurred conveniently and directly.

Iii. When to draw a data flow chart

In the demand analysis stage, in order to gain a conceptual understanding of the new system framework, we need to model the new system. The requirement is modeled to obtain the analysis model. The Structural Analysis Method in demand analysis is characterized by data flow graphs to help people understand and analyze problems.

4. How to draw a data flow chart

(1) determine the input and output of the system

As it may be difficult to figure out which functions are included in the system at the moment, the scope can be as large as possible and all possible content can be included. In this case, you should learn "what data the system accepts from the outside", "what data the system sends to the outside world", and then draw the periphery of the data flow chart based on the user's response.

(2) Draw the system's top-layer data flow diagram from the external to the internal

First, connect the system's input and output data with a series of processes. Where the value of the data stream changes, it is a process. Next, name each processing item. Then, name the data between processes. Finally, name the file.

(3) layer-by-layer decomposition from top to bottom to draw a hierarchical data flow diagram

For large systems, in order to control complexity and make it easy to understand, we need to use top-down layer-by-layer decomposition, that is, a data flow chart is divided into several data flow graphs by means of stratified representation.

V. Data Flow Chart instances

Data Flow Diagram of the data room Charging System