现在的一切都是为将来的梦想编织翅膀，让梦想在现实中展翅高飞。
Now everything is for the future of dream weaving wings, let the dream fly in reality.
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Advanced skills in system architecture design·Structured requirements analysis-data flow diagram
1. Basic concepts of data flow diagram
- Entities
Entities may be:
(1) Personas: such as customers, administrators, supervisors, managers, teachers, students
(2) Organizations : such as banks, suppliers, fundraising agencies
(3) External systems: such as banking systems, payroll systems , Backend database (when middleware is to be developed) - Storage
Text characteristics of storage: "**File", "**Table", "**Library", "**List", "**File" - Data flow
1. Data balance principle
(1) Compare the top-level graph with the 0-layer graph to see if there is a data flow that is present in the top-level graph but not in the 0-layer graph, or vice versa.
(2) Check each processing in the figure to see if there is only in but no out, or only out and no in, or the corresponding output cannot be generated based on the input data.
2. Match the required title description with the diagram.
Every sentence in the description can have a corresponding relationship with the diagram. After identifying the entities and data flows in the description, it is easy to narrow the corresponding scope and find errors. - Processing name
Processing is used to process data streams, so to supplement the processing name, you can identify the data streams involved in the processing in the description, and then look for "verb + noun" in the sentence where the data stream name islocated . Structure, analyze whether it can be processed.
"Verb + noun" such as: generating reports, issuing notifications, correcting homework, and recording scores. Of course, this is only a common situation, and there are exceptions, such as logistics tracking and user management.
2. Requirements Analysis (SA) - Data Flow Diagram (DFD)
3. Balance principle of data flow diagram
