What is an ER Diagram ?

An Entity Relationship (ER) Diagram is a type of flowchart that illustrates how "entities" such as peopl, objects or concepts relate to each other within a system. ER Diagrams are most often used to design or debug relational database in the fields of software engineering, business information system, education and research.

Also known as ERDs or ER Models, they use a defined set of symbols such as rectangles, diamonds, ovals and connecting lines to depict the interconnectedness of entities, relationships and their attributes. They mirror grammatical structure, with entities as nouns and relationships as verbs.

ER diagrams are related to data structure diagrams (DSD), which focus on the relationships of elements within entities instead of relationships between entities themselves. ER diagrams also are often used in conjunction with data flow diagrams (DFD), which map out the flow of information for processes or systems.

Diagramming is quick and easy with draw.io, Lucidchart, smartdraw.com. It's quick, easy and completely free.

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Mapping Natural Language

ER components can be equated to parts of speech.

• Common Noun: Entity Type, Example: Student

• Proper Noun: Entity, Example: Syed Jafer

• Verb: Relationship Type, Example: Enrolls ( Such as in course, which would be another entity type )

• Adjective: Attribute for entity, Example: Piano

• Adverb: Attribute for relationship, Example: Digitally.

🥁 You might need to revisit this again at the end of this chapter.

Let us consider the example of University Management System.