A data-modeling approach that describes a domain as entities, their attributes, and the relationships between them, most often expressed as entity-relationship diagrams (ERDs) used to design and communicate the structure of a database or system.
Entity Relationship
Entity Relationship modeling is a way of describing a domain as a set of entities, the attributes that define them, and the relationships that connect them. Introduced by Peter Chen in 1976, it is most often expressed as an entity-relationship diagram (ERD) — the boxes-and-lines picture teams use to design a database or reason about the structure of a system before writing any code.
- Entities - The things a system tracks, such as a customer, an order, or a product, each with its own set of attributes.
- Relationships - The named associations between entities, carrying cardinality like one-to-one, one-to-many, or many-to-many.
- Attributes and keys - The properties that describe an entity and the identifiers that make each instance unique.
- The diagram as shared language - An ERD lets engineers, analysts, and stakeholders agree on data structure before it hardens into schema.
In API work, entity-relationship thinking is the quiet groundwork beneath the resources an API exposes. The entities and relationships in a data model map closely to the paths, schemas, and links that show up in an OpenAPI definition or a JSON Schema document, and getting that model right early keeps an API’s surface coherent. As agents traverse APIs by following relationships between resources, a clear entity-relationship foundation is what makes that navigation predictable.
