ER diagram and data flow diagram of experimental equipment management system

E-R model approach to the abstract description of the real world provides a powerful tool, which represents the conceptual model is the basis of a variety of data models, management information systems, a variety of data to a real form of response, easy to handle the data, analysis, processing, and ultimately the information required for decision-making!

I think that when analyzing E-R diagrams and data flow diagrams are two parallel methods of analysis.

E-R diagrams are more commonly used when analyzing databases.

If you want to classify them, there is a hierarchy

E-R diagrams, data flow diagrams, and data dictionaries

For more details, you can refer to the specialized books on information systems development.

E-R diagrams, data flow diagrams, and data dictionaries.