Editing Data modeling (section)

=== Entity–relationship diagrams ===
{{main|Entity–relationship model}}
[[File:B 5 1 IDEF1X Diagram.jpg|thumb|550px|right|Example of an [[IDEF1X]] entity–relationship diagrams used to model IDEF1X itself. The name of the view is mm. The domain hierarchy and constraints are also given. The constraints are expressed as sentences in the formal theory of the meta model.<ref name="FIPS184">[http://www.itl.nist.gov/fipspubs/idef1x.doc FIPS Publication 184] {{Webarchive|url=https://web.archive.org/web/20131203223034/http://www.itl.nist.gov/fipspubs/idef1x.doc |date=December 3, 2013 }} released of IDEF1X by the Computer Systems Laboratory of the National Institute of Standards and Technology (NIST). December 21, 1993.</ref>]]
There are several notations for data modeling. The actual model is frequently called "entity–relationship model", because it depicts data in terms of the entities and relationships described in the [[data]].<ref name="WBD04"/> An entity–relationship model (ERM) is an abstract conceptual representation of structured data. Entity–relationship modeling is a relational schema [[database model]]ing method, used in [[software engineering]] to produce a type of [[conceptual schema|conceptual data model]] (or [[semantic data model]]) of a system, often a [[relational database]], and its requirements in a [[Top-down and bottom-up design|top-down]] fashion.

These models are being used in the first stage of [[information system]] design during the [[requirements analysis]] to describe information needs or the type of [[information]] that is to be stored in a [[database]]. The [[data model]]ing technique can be used to describe any [[Ontology (computer science)|ontology]] (i.e. an overview and classifications of used terms and their relationships) for a certain [[Domain of discourse|universe of discourse]] i.e. the area of interest.

Several techniques have been developed for the design of data models. While these methodologies guide data modelers in their work, two different people using the same methodology will often come up with very different results. Most notable are:

* [[Bachman diagram]]s
* [[Barker's notation]]
* [[Entity–relationship model|Chen's notation]]
* [[Data Vault Modeling]]
* [[Extended Backus–Naur form]]
* [[IDEF1X]]
* [[Object-relational mapping]]
* [[Object-Role Modeling]] and [[FCO-IM|Fully Communication Oriented Information Modeling]]
* [[Relational Model]]
* [[Relational Model/Tasmania]]