Editing Entity–relationship model (section)

{{Short description|Model or diagram describing interrelated things}}
{{More citations needed|date=November 2016}}
[[File:ER Diagram MMORPG.png|thumb|upright=1.75|An entity–attribute-relationship diagram for an [[MMORPG]] using Chen's notation]]

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 [[wikt:entity|entities]] (instances of those entity types).

In [[software engineering]], an ER model is commonly formed to represent things a business needs to remember in order to perform [[business process]]es. Consequently, the ER model becomes an abstract [[data modeling|data model]],{{sfn | Bagui | Earp | 2022 | loc=§4.2.1 | p=72}} that defines a data or information structure that can be implemented in a [[database]], typically a [[relational database]].

Entity–relationship modeling was developed for database and design by [[Peter Chen]] and published in a 1976 paper,<ref name=Chen>{{cite journal  |last=Chen  |first=Peter |author-link = Peter Chen |title = The Entity-Relationship Model - Toward a Unified View of Data |journal = ACM Transactions on Database Systems| volume = 1 | issue = 1 |pages = 9–36 | date = March 1976 | doi = 10.1145/320434.320440|citeseerx=10.1.1.523.6679 |s2cid=52801746 }}</ref> with variants of the idea existing previously.<ref>A.P.G. Brown, "Modelling a Real-World System and Designing a Schema to Represent It", in Douque and Nijssen (eds.), ''Data Base Description'', North-Holland, 1975, {{ISBN|0-7204-2833-5}}.</ref> Today it is commonly used for teaching students the basics of database structure. Some ER models show super and subtype entities connected by generalization-specialization relationships,<ref>{{Cite web|url=https://docs.microsoft.com/en-us/previous-versions/tn-archive/cc505839(v%3dtechnet.10)|title=Lesson 5: Supertypes and Subtypes|website=docs.microsoft.com}}</ref> and an ER model can also be used to specify domain-specific [[ontology (information science)|ontologies]].