#The data flow diagram is completed during the conceptual structure design phase of the database system design process.
Introduction to relevant knowledge points:
What is a data flow diagram?
Data flow diagram or data flow diagram (Data Flow Diagram), abbreviated as DFD. Data flow diagram DFD is a graphical tool that describes the data flow in the system. It marks the logical input and logical output of a system, as well as the processing required to convert logical input into logical output.
The data flow diagram is not a traditional flow chart or block diagram, and the data flow is not a control flow. A data flow diagram describes a system from the perspective of data, while a block diagram describes the system from the perspective of the staff who process the data.
Data flow diagram graphically depicts the movement and transformation process of data flow from input to output from the perspective of data transmission and processing.
The data flow chart includes:
1. Data symbols that indicate the existence of data. These data symbols can also indicate the media used by the data;
2. Processing symbols that indicate the processing performed on the data. These symbols can also indicate the machine functions used in the processing;
3. Specify the data flow between several processes and/or data media. Streamline symbols;
4, special symbols that facilitate reading and writing data flow diagrams.
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