Editing Entity–relationship model (section)

== Limitations ==
* An ER model is primarily conceptual, an ontology that expresses predicates in a domain of knowledge. 
* ER models are readily used to represent relational database structures (after Codd and Date) but not so often to represent other kinds of data structure (such as data warehouses and document stores)
* Some ER model notations include symbols to show super-sub-type relationships and mutual exclusion between relationships; some do not.
* An ER model does not show an entity's life history (how its attributes and/or relationships change over time in response to events). For many systems, such state changes are nontrivial and important enough to warrant explicit specification.
* Some{{Who|date=June 2012}} have extended ER modeling with constructs to represent state changes, an approach supported by the original author;<ref>P. Chen. [https://doi.org/10.1007%2F11901181_1 Suggested research directions for a new frontier: Active conceptual modeling]. ER 2006, volume 4215 of Lecture Notes in Computer Science, pages 1–4. Springer Berlin / Heidelberg, 2006.</ref> an example is [[Anchor Modeling]]. 
* Others model state changes separately, using state transition diagrams or some other [[process modeling]] technique.
* Many other kinds of diagram are drawn to model other aspects of systems, including the 14 diagram types offered by [[Unified Modeling Language|UML]].<ref>[https://aisel.aisnet.org/jise/vol17/iss1/9  Carte, Traci A.; Jasperson, Jon (Sean); and Cornelius, Mark E. (2020) "Integrating ERD and UML Concepts When Teaching Data Modeling," Journal of Information Systems Education: Vol. 17 : Iss. 1, Article 9.]</ref>
* Today, even where ER modeling could be useful, it is uncommon because many use tools that support similar kinds of model, notably class diagrams for OO programming and data models for relational [[database management system]]s. Some of these tools can generate code from diagrams and reverse-engineer diagrams from code.
* In a survey, Brodie and Liu<ref>[https://www.deri.ie/content/power-and-limits-relational-technology-age-information-ecosystems The power and limits of relational technology in the age of information ecosystems] {{Webarchive|url=https://web.archive.org/web/20160917100748/https://www.deri.ie/content/power-and-limits-relational-technology-age-information-ecosystems |date=2016-09-17 }}. On The Move Federated Conferences, 2010.</ref> could not find a single instance of entity–relationship modeling inside a sample of ten Fortune 100 companies. Badia and Lemire<ref>A. Badia and D. Lemire. [http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.297.4916&rep=rep1&type=pdf A call to arms: revisiting database design]. Citeseerx,</ref> blame this lack of use on the lack of guidance but also on the lack of benefits, such as lack of support for data integration.
* The [[enhanced entity–relationship model]] (EER modeling) introduces several concepts not in ER modeling, but are closely related to [[object-oriented]] design, like [[is-a]] relationships.
* For modelling [[temporal database]]s, numerous ER extensions have been considered.<ref>{{cite journal | last1 = Gregersen | first1 = Heidi | first2 = Christian S. | last2 = Jensen | title = Temporal Entity-Relationship models—a survey | citeseerx = 10.1.1.1.2497 | journal = IEEE Transactions on Knowledge and Data Engineering| volume = 11 | issue = 3 | date = 1999 | pages = 464–497 | doi = 10.1109/69.774104 }}</ref> Similarly, the ER model was found unsuitable for [[multidimensional database]]s (used in [[OLAP]] applications); no dominant conceptual model has emerged in this field yet, although they generally revolve around the concept of [[OLAP cube]] (also known as ''[[data cube]]'' within the field).<ref name="Rafanelli2003">{{cite book|editor=Maurizio Rafanelli|title=Multidimensional Databases: Problems and Solutions|year=2003|publisher=Idea Group Inc (IGI)|isbn=978-1-59140-053-0|chapter-url=http://torlone.dia.uniroma3.it/pubs/idea03.pdf|chapter=Conceptual Multidimensional Models|author=RICCARDO TORLONE}}</ref>