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An entity–relationship model (or ER model) describes interrelated things of interest in a specific domain of knowledge. A basic ER model is composed of entity types (which classify the things of interest) and specifies relationships that can exist between entities (instances of those entity types).
The enhanced entity–relationship (EER) model (or extended entity–relationship model) in computer science is a high-level or conceptual data model incorporating extensions to the original entity–relationship (ER) model, used in the design of databases.
Entity–relationship modeling is a database modeling method, used to produce a type of conceptual schema or semantic data model of a system, often a relational database, and its requirements in a top-down fashion. Diagrams created by this process are called entity-relationship diagrams, ER diagrams, or ERDs.
A sample Entity-relationship diagram using Chen's notation. A sample Entity-relationship diagram. A sample ER diagram.}} {{ko|ER 다이어그램 예제.}} {{ru|Простая ER-мо
Sequence diagrams are sometimes called event diagrams or event scenarios. For a particular scenario of a use case, the diagrams show the events that external actors generate, their order, and possible inter-system events. [2] The diagram emphasizes events that cross the system boundary from actors to systems.
A relationship in which an instance of either entity can be related to any number of instances of the other. View levels Three levels of view are defined in IDEF1X: entity relationship (ER), key-based (KB), and fully attributed (FA). They differ in level of abstraction. The ER level is the most abstract.
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