Entity Relationship Diagram Concepts
Entity relationship diagrams (ERDs) are the second major document (the first is the data f low diagram) that is developed when using the traditional approach to system analysis and design. When designing a new system, the systems analyst first identifies all of the processes and data needed within a system. The system processes, the f low of data between the processes, the data stores, and the external entities are captured in a data flow diagram (DFD).
Data moving through a system is depicted on a DFD by data flows. Each data f low contains a variety of data items. These are the bits of data that are the inputs to a process and the outputs from a process. When these bits of data are at rest, they are contained ...
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