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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.
Relationships can be thought of as verbs, linking two or more nouns. [7] Examples include an owns relationship between a company and a computer, a supervises relationship between an employee and a department, a performs relationship between an artist and a song, and a proves relationship between a mathematician and a conjecture.
Each element in the weak entity set must have a relationship with exactly one element in the owner entity set, [1] and therefore, the relationship cannot be a many-to-many relationship. Two entities can be associated without either being classified as weak, even if one depends on the other, as long as each has its own unique attribute. [1]
The C4 model documents the architecture of a software system, by showing multiple points of view [5] that explain the decomposition of a system into containers and components, the relationship between these elements, and, where appropriate, the relation with its users. [3] The viewpoints are organized according to their hierarchical level: [2] [3]
Entity-relationship model; Usage on en.wikiversity.org Concept mapping; Usage on hu.wikipedia.org ER-modell; Usage on lv.wikipedia.org ER diagrammas; Usage on no.wikipedia.org Entitet–relasjonsmodell; Usage on pt.wikiversity.org Observatório de dados/BI/Capacidade/Junção; Usage on ro.wikipedia.org Modelul entitate-asociere; Usage on simple ...
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.
The entity–relationship model proposes a technique that produces entity–relationship diagrams (ERDs), which can be employed to capture information about data model entity types, relationships and cardinality. A Crow's foot shows a one-to-many relationship. Alternatively a single line represents a one-to-one relationship. [4]
Barker's notation refers to the ERD notation developed by Richard Barker, Ian Palmer, Harry Ellis et al. whilst working at the British consulting firm CACI around 1981. The notation was adopted by Barker when he joined Oracle and is effectively defined in his book Entity Relationship Modelling as part of the CASE Method series of books.