Talk:Entity–relationship model

message: " what is the meaning of 428 BC near his name?" Der Volks-Brockhaus, F.A. Brockhaus Wiesbaden. 196646.114.104.43 (talk) 13:01, 3 April 2020 (UTC)
thread_title:  Aristotle was born in 384 and died in 322 BC 

message: "...for instance, your entry in the database could point to several entries for each of the phone numbers that are yours" I can't understand what this is trying to say. First off, what does it mean "your entry".
--206.87.81.34 (talk) 08:08, 2 November 2012 (UTC)
thread_title:  Third sentence very unclear 

message: In 13 years doing database work in the United States, I've Foot notation everywhere.  This part needs a citation: "Usage of Chen notation is more prevalent in the United States, while Crow's Foot notation is used primarily in the UK."
205.173.24.4 (talk) 18:58, 17 November 2010 (UTC)
thread_title:  Prevalence of Crow's Foot Notation 

message: I must say that I agree at least on the lack of clarity of the first sentence. Either its meaning is wrong or it is poorly written. Whichever it is, the first sentence of the introduction is misleading to the least. 194.221.74.7 08:54, 8 June 2006 (UTC)
replies: text: I agree - calling an entity a 'discrete object is not very accurate, but then again, what would be a more accurate term?  Rp 10:20, 10 July 2006 (UTC)

text: You have a good point there - I think conversion from ER model to logical relational model must be treated if only to make the point that the ER model is not an informal drawing technique but has a sound formal basis. Rp 10:20, 10 July 2006 (UTC)
thread_title:  Common Symbols Section Needs Work 

message: Any chance someone could mock up a set of images showing what these symbols are supposed to look like?  Describing them is all well and good, but a picture can be worth a thousand words.  :)  Thanks,  Eirikr 03:45, 8 Apr 2005 (UTC)
replies: text: I've added a first example diagram. I'd like to include some more images but I'm having trouble deciding which examples would best clarify some of the text. Also, I'm wondering if it'd make any sense to upload the original Dia files and refer to them from the Image:erd-*.png nodes for if anyone else wants to change something in the coloring or whatnot... --BigSmoke 16:27, 12 Jun 2005 (UTC)
thread_title: Symbols

message: As far as I know there are multiple ways of drawing ER diagrams. I use arrows. Yet the article implies that'Bold text' there's only this one way.
Where's the explanation/links about ER 2004? --Khokkanen 12:53, 10 June 2006 (UTC)
replies: text: I have added a section entitled Alternative diagramming conventions with a diagram and explanation for <B>Crow's Feet</B> notation.  I encourage you all to post up similar descriptions of the notations you prefer.  See also Diagram is not standard section below.  --Matthew 1130 13:05, 30 December 2006 (UTC)
replies: text: That's not the classical Crow's Foot notation, it's IDEF1X. -- EmmetCaulfield 11:20, 6 November 2007 (UTC)
replies: text: I am nearly certain it should be "Crow's Foot", not "Crow's Feet". Sam Tomato (talk) 05:56, 12 November 2016 (UTC)
thread_title:  Diagrams and ER 2004 

message: This diagram is not remotely similar to the methods used by nearly all of the major ER tools in use today.  IDEF1X is far and away a more common mechanism, as are derivatives of that method that vary primarily in the symbols used to indicate n-ary relationships.  
I suggest we replace this article with one that is similar to the article referenced by the IDEF1X link (US Navy, I think).  This article is absolutely useless for practitioners and students of ER models. User:nickmalik 11:47 15 Oct 2006 {PDT)
: I strongly disagree. Since the article's subject is the Entity-Relationship Model it should use the classical notation. Any other choice would be somewhat arbitrary as there are many tools and many dialects and none of them is really predominant. Most (database) textbooks I know use the classical notation. -- Jan Hidders 21:39, 15 October 2006 (UTC)
replies: text: I suppose we should use Roman Numerals for math articles since they are a more "classical representation". I have been involved with data modeling for nearly 20 years and have never seen an ER diagram like that. I agree that IDEF1X is generally considered the best representation.  —The preceding unsigned comment was added by 74.242.64.129 (talk) 19:54, 17 December 2006 (UTC)

text: Yes, that is correct. Why? -- Jan Hidders 21:29, 18 October 2006 (UTC)

text: I suspect we should replace the Artist-Song relationship with a Product-Recommendation relationship, because Artist-Song is really a many-to-many relationship if we are going to be true to the real world, and we need a one-to-many relationship to best illustrate the diagramming convention.  My one concern is whether the editor who originally created the Artist-Song diagram can modify it to Product-Recommendation?  Matthew 1130 12:53, 19 December 2006 (UTC)

text: Except it should be "Crow's Foot", not "Crow's Feet", right?. Sam Tomato (talk) 05:57, 12 November 2016 (UTC)

text: No, the Chen style is NOT the original. Consultants at Scicon and CACI in the UK were using a kind of crow's foot notation in the early 1970s. But they didn't write academic papers about it, so it's hard to prove. ER modelling was invented by practitioners, not by Chen; Chen's contribution was to formalize the ideas and introduce them to an academic audience. Mhkay (talk) 07:33, 8 April 2009 (UTC)
thread_title:  Diagram is not standard 

message: I doubt that an Entity-relationship model can be called a data model. It is a method to design data models. --Udo Altmann 13:42, 18 Oct 2004 (UTC)
replies: text: If it were a method it would be called the Entity-Relationshp Method. The researchers at the ER 2004 would be highly amazed by your claim that the ER model is not a data model. -- Jan Hidders 11:05, 19 Oct 2004 (UTC)
replies: text:  Sorry for again starting a method discussion. The introduction sounds as if the ERModel is a data model for a data model - a meta model - which for me has an implicit methodological aspect. I think this was, what caused my discomfort. Wouldn't it be simplier (and still correct) to say "A Entity-Relationship model is a high-level description of a conceptual data model. Entity-Relationship models include graphical notations for representing such data models in the form of entity-relationship diagrams". --Udo Altmann 09:24, 1 Nov 2004 (UTC)
replies: text:  It would be incomplete. As already explained, the ER model is a meta model (with a graphical notation and some semantics), so that is of course what the introduction should explain. Why are you uncomfortable with that? I also fail to see why you connect that with a methodological aspect because that link is very very weak. There is no fixed method to arrive at your model and there is no fixed method to go from your ER diagram to your relational model, and, as was already explained, the scope of the ER model is much wider than just a method to arrive at your relational model. So what then is it exactly that you mean with this mysterious "methodological aspect"? It's still as if you want to believe that the ER model is a method. Please don't. Apart from being incorrect that view is much too narrow and does unjustice to the ER model. :-) -- Jan Hidders 13:53, 2 Nov 2004 (UTC)
thread_title:  Model -vs- Method 

message: The link to Dr. Chen's paper in the references section is broken.
The link to Richard Barker references a page about a Hartlepool FC player Richie Barker User:NigelThomas  —Preceding unsigned comment added by 212.58.233.129 (talk) 14:31, 7 January 2008 (UTC)
thread_title:  Broken Links 

message: I fixed the image of the crow feet, with the vertical line and the O being the wrong way round and uploaded the new version. Bencoder 17:16, 13 May 2007 (UTC)
replies: text: That should be Crow's Foot, not crow feet. Sam Tomato (talk) 06:03, 12 November 2016 (UTC)
thread_title:  Crow feet image problem 

message: The beginning of the article doesn't look encyclopedic. May I suggest: "ERM is a technique for the structure design of data on databases" or something like that? It would say the same it does now, but in a different order... Magdalena B. 12:28, 9 July 2007 (UTC)
thread_title:  Beginning 

message: Visio is mentioned as a free tool to create diagramms, but the Link directs to Microsoft Visio. Is there a free tool with the same name? (I can't find one)  —Preceding unsigned comment added by 138.232.248.27 (talk) 02:56, 16 December 2007 (UTC)
thread_title:  Visio Free software?? 

message: According to the Information Engineering article, "Information Engineering ... is an approach to designing and developing information systems". It's not therefore an example of a notation "more typically employed in logical and physical database design". The IE methodology does use entity-relationship diagrams, and I've added a wikilink to it in the Crow's Foot section to replace the wikilink in the introduction. --Northernhenge (talk) 09:50, 11 April 2008 (UTC)
thread_title:  Rationale for removing Information Engineering from database sentence in introduction 

message: Some wereks ago I trimmed a long list of software programs supporting supporting Entity-relationship models, see here, to the following normal size text:
:There are lot of ER diagramming tools. Some of the proprietary ER diagramming tools are Avolution, ConceptDraw, ER/Studio, ERwin, DeZign for Databases, MEGA International, OmniGraffle, Oracle Designer, PowerDesigner,  Rational Rose, RISE Editor, SmartDraw, Sparx Enterprise Architect, SQLyog, Toad Data Modeler, Microsoft Visio, and Visual Paradigm 
:Some free software ER diagramming tools that can interpret and generate ER models, SQL and do database analysis are MySQL Workbench and StarUML. Some free software diagram tools which can't create ER diagrams but just draw the shapes without having any knowledge of what they mean or generating SQL are Kivio and Dia (software)
Now I resored it again, but I don't understand, why it was removed here in the first place? There shouldn't be a list of over 50 tools, half of it not even notable enough to have a Wikipedia article of it's own. Lists like that are an invitation to keep spamming this article, with every new unknown tools. This is not acceptable in Wikipedia. -- Marcel Douwe Dekker (talk) 15:49, 7 November 2008 (UTC)
thread_title:  List of linkspam (again) trimmed to a normal size 

message: Can anyone justify the Bachmann diagram? I definitely recall that in Bachmann diagrams, the arrow-head goes from "owner" to "member", that is from the "1" end of a relationship to the "many" end: I remember people criticising it for that. And I don't know what these open and solid circles are doing on the line. Arguably it doesn't really have a place here anyway, because the Codasyl model was never presented to the world as an ER model or as a data modelling technique (as destinct from a database model).
Mhkay (talk) 07:39, 8 April 2009 (UTC)
thread_title:  Bachmann diagram 

message: I made another diagram and put it here: 
Wooptoo (talk) 17:55, 30 May 2009 (UTC)
thread_title:  another diagram 

message: According to http://rapidapplicationdevelopment.blogspot.com/2007/06/entity-relationship-diagram-example.html (not a reliable source, I know)
the crow's foot notation for person - location should be the other way around. 
LOCATION has zero-to-many PERSONS born there.
PERSON has one and only one birthplace.
Now I've confused myself to the extent that I can't decipher the artist-performs-song pic.
So confused. Enlightened ones, take corrective measures if you please. No need to reply to this, I probably won't read the reply. Primary key (talk) 17:49, 12 June 2009 (UTC)
replies: text: The notation looks fine to me. Libcub (talk) 03:38, 13 June 2009 (UTC)
thread_title:  Crow's foot example - incorrect? 

message: I was stunned to see such a strange example of an ERD!  I came to Wikipedia for some clarity and went away dumbfounded.  There is so much detailed, and sometimes erroneous, disagreement that, if this discourse is held to be a serious source for producing ERDs, then Heaven help data modelling!  —Preceding unsigned comment added by Vortigern one (talk • contribs) 17:19, 18 November 2009 (UTC)
replies: text: Can you be more specific on your confusion?  Dumbfounding people is not the goal of Wikipedia articles, but they can't ignore the fact that these languages, like all languages, have dialects and complicated family relationships. Rp (talk) 08:53, 26 March 2010 (UTC)
thread_title:  Entity Relationship Modelling Principles 

message: The fact that StarUML, a UML modeling tool, was listed in this article as a ER modelling tool for two years suggests that either I'm unaware of StarUML's true capabilities or it would be worthwhile to add a section explaining the differences between ER models and UML class models in detail.  Mind if I add such a section? Rp (talk) 08:53, 26 March 2010 (UTC)
thread_title:  Comparison with UML class diagrams 

message: I'm guessing "ERA model" is just a more uncommon name for "ER model"? The reason I ask is that a newsgroup I read had a post with someone asking for an "ERA modeler", which I looked up and found this entry on Encyclopedia.com. But I was unable to find an entry for ERA model or Entity-Relationship-Attribute on Wikipedia. I've created both those pages and redirected them to here. But I just wanted to make sure there wasn't some hidden distinction between an ER model and an ERA model. Otherwise, I guess ERA diagram should probably redirect here as well.--Subversive Sound (talk) 17:44, 13 May 2010 (UTC)
thread_title:  ER model versus ERA model 

message: The overview has recently been updated so the following comments are no longer significant!  April 2012  — Preceding unsigned comment added by 208.44.95.13 (talk) 18:41, 9 April 2012 (UTC)
replies: text: Not so. The overview is rubbish. The recent edits have made it worse. Far too many ignorant people have contributed to this page. Mhkay (talk) 18:53, 9 April 2012 (UTC)

text: You will need to further quality your "wrong".  The approach to distinguish separate design phases, in which a conceptual, logical and physical model are created in turn, is common in database design courses.  It is not universally taught or followed, but that does not make it "wrong".  I do agree that it is wrong for this article to be so casual and take it for granted, but isn't exactly the only text on database design that does this.  As to the difference between grammar and technique, I think this is a matter of definitions: your "grammar" is another person's "technique".  Anyhow, there is much room for improvement.  Looking forward to your improvements or suggestions for them. Rp (talk) 16:02, 26 January 2011 (UTC)

text: "People didn't even realize that ER could be bastardized into a conceptual modeling grammar until well after this notation was developed." I know it's tough to ask you to prove a negative, but I wonder if you can explain why you think this? The consultants I was working with in the mid 1970s certainly considered that they were formalising notations for conceptual modelling that were independent of logical database design. Also, it's unclear what you mean by "bastardized". You claim that ER "is" a grammar, then you say the grammar is a "bastardization" of ER. Mhkay (talk) 16:14, 26 January 2011 (UTC)
thread_title:  Overall Wrongness 

message: The article starts from the wrong premise. It is based on Peter Chen's view of this topic. Much original thinking had already taken place within IBM and some London based consultancies, to my knowledge and probably elsewhere too. In the interests of clarity it would help to recognise the history of the topic, which the article has failed to do. 
The history below is much better than nothing:
History
ER Diagrams were first introduced by Charles Bachman. "Bachman Diagrams" described data structures, however, he did however go further and recognised the need to model at a higher level of abstraction. 
“… entity to mean a particular object being considered; the term entity class will mean an entire group of entities which are sufficiently similar, in terms of attributes that describe them, to be considered collectively … entity set … associates a group of entities in one entity class with one entity of a different entity class in a subordinate relationship” page 4 of "Bachman, C. W. (1969) Data Structure Diagrams. DATA BASE 1(2): 4-10" 
See a fuller discussion of the whole topic of Bachman and Chen diagramming in "The Entity Relationship Model And Practical Data Modelling By Steve Hitchman 2004, Journal of Conceptual Modeling, April 2004". 
ER diagrams were popularised by Dr. Pin-Shan (Peter) Chen in 1976, but he drew on the previous work of his colleagues, one of whom was Charles Bachman. 
: I think Chen is usually credited as the originator because he was the first person to have an article on entity-relationship models published in the academic literature; he was also the first to formalize them. The earlier work (by people like Ian Palmer of Scicon) was practical consultancy and it's now very hard to find citations. Mhkay (talk) 18:58, 9 April 2012 (UTC)
replies: text: Wait a minute: Bachman diagram and Data structure diagram (which is what Bachman named his diagrams when he introduced them in 1969) have their own article(s); you may want to start there, e.g. by merging them.  I do agree that a more unified perspective on database diagramming and information diagramming is necessary, but in IT we all know only the languages we've been taught, even if the neighbours use a different one to say the same things.  So I'm not sure a single article would suffice.  However at least some notes on developments and more crosslinking would be in order. Rp (talk) 22:58, 17 August 2011 (UTC)
thread_title:  REQUIRES A TOTAL REWRITE  

message: The sub-section on 'Cardinalities' assumes much information not provided within the article, and uses the following terms without explanation or motivation:
*cardinality,
*look-across,
*same-side,
*minimum cardinality,
*optionality,
*maximum cardinality,
*crows foot (sic),
*n-ary relationship,
*order (of relationship),
*degree,
*transformation,
*extension,
*mechanism,
*simple mechanism. 
And the two asides in parentheses only compound the jargon problem ...
The whole section 'Relationships, roles and cardinalities' smacks of either original research or personal opinion.  At the very least, it needs some citations to support its contentions.
If the whole article is seen as an intelligent layman's overview of E-R modelling, the material presented throughout (but not in this sub-section) is quite hard enough.  This sub-section on 'Cardinalities' is pitched at completely the wrong level. 
As a seasoned ADP | EDP | DP | Computing | IT | ICT professional, I ask myself: What problem is the sub-section on 'Cardinalities' trying to solve?  I can only conclude it's driving towards the quote from Feinerer, referencing Hartmann:
'Problems arise if we operate under the look-across semantics as used for UML associations ... different transformations fail.'
 
This surely is, at once, both too abstract and too low-level a consideration for the "intelligent layman" who has read the previous material? 
If all the sub-section manages to say is that "look-across semantics don't work", or "... don't properly represent the meanings of the relations between entities", shouldn't the article then say what we DO about it?
For the present, I suggest scrapping all the text under the sub-heading "Cardinalities" and replacing it with an explanation of:
* what the term 'cardinality' means in E-R models, and
* why we choose to represent all possible (finite mathematical) cardinalities by only the values 0, 1 and M(any).
yoyo (talk) 17:38, 8 April 2012 (UTC)
thread_title:  Problems with 'Cardinalities' sub-section 

message: I started using Entity Modeling in approximately 1974 at the City of Westminster in London. This was based on work at ICL by Harry Ellis and David Gradwell et al. David Gradwell may well be able to provide even earlier history. A lot of the pioneers were related to the Data Dictionary Working Group within the British Computer Society at the time. This predated the Chen paper but Chen was usually considered the academic father of ER modeling simply because he published one of the first papers on the subject and it was very influential. His use of Relationships as first class objects was generally rejected at the time, as it didn't prove very useful for the practicioners. It supports n-ary relationships and the databases of the time didn't have much use for such relationships. 
The techniques and notation used in ER modeling were developed by the database practicioners of the time. The problem that was being addressed was the inflexibility of CODASYL databases, such as DMS1100 (Univac) and IDMS which I think was used by ICL, hence their interest in ER modeling. You had to get the schema right as it was very difficult to alter it once the database was in production. This lead to the use of ER modeling as a basis for database design so that the schema would be well designed initially.
After Westminster, I joined CACI in the Netherlands and participated in the development of ER modeling with Ian Palmer, David Gradwell, Bernie Benetto and others. We introduced concepts and notation for entity subtypes and supertypes, time based data (ways to model dynamic data), relationship optionality and inclusive/exclusive relationships. At the time, CACI had two database cunsultancy offices in Europe, one in the UK and one in the Netherlands and they worked closely together on ER modeling. After that came Richard Barker, Rosemary Rock-Evans and others at CACI who documented the approach. From there it moved to James Martin Associates and then to Oracle.
Bachman's early work may have had some influence on ER modeling but it would have had to have been very early and relatively limited as we considered his approach more of a different and rival approach at the time.  — Preceding unsigned comment added by Djwdjw123 (talk • contribs) 23:47, 7 November 2012 (UTC)
thread_title:  Early History 

message: For many systems, the possible changes to the information contained are nontrivial and important enough to warrant explicit specification.  - Could you elaborate more?
Sumdumboot (talk) 05:15, 28 March 2013 (UTC)
thread_title:  Limitations 

message: Does anyone else feel like the resource linked to from the external links section is poor quality? The information is helpful but the formatting and readability issues seem to detract from the ability for a normal user to find the page useful.  Any suggestions for a better resource?
Bhanks (talk) 20:49, 9 July 2013 (UTC)
replies: text: The tool you like to use has been appropriately removed as spam. --Ronz (talk) 19:46, 17 July 2013 (UTC)
thread_title:  Crows foot notation external link 

message: Which is preferable for the lead sentence?
or some thing like:
Jojalozzo 18:01, 11 March 2014 (UTC)
thread_title:  Lead sentence structure 

message: The introduction still doesn't make much sense:
* ER models do not describe business processes: they describe what can be, not how it changes or can change. You can see this from the example given: a building or an apartment is not a process. (They can be relevant to a business process, and describing all things relevant to a business process goes some way towards describing that process, but it is not the same thing.)
* There should be a better distinction between ER models (information schemas) and instances of such models (actual information structured described according to such schemas).  For instance, it should be clarified that a description of a particular set of buildings and apartments will be an instance of an ER model describing buildings and apartments in general.
Rp (talk) 12:23, 24 June 2015 (UTC)
thread_title:  Introduction still wrong 

message: Entity class redirects to this article, but the term isn't mentioned, and I have no idea what it means. Can anyone explain? Rp (talk) 18:55, 12 July 2015 (UTC)
thread_title:  What is an ''entity class''? 

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thread_title:  External links modified 

message: I like the newly added section Modelling issues, but it needs further improvement:
* These issues were mentioned by Codd - his article should be referenced and possibly quoted.
* From the present text, I don't understand what the problems are.  It should be clarified, preferably with examples.
* The present text suggests that these problems are limitations or drawbacks of ER modeling; it suggests that ER models correcting these problems do not exist.  From the referenced text, it becomes clear that this is not the case: correct models for these situations do exist.  This should be made clear. Rp (talk) 18:27, 21 October 2016 (UTC)
thread_title:  Modelling issues 

message: Is the page Crow's Foot Notation truly authoritive (yes I know I spell "authoritive" differently than most)?  It looks like someones' college notes. What qualifies bernatja at the University of Regina as an authority? Or can I just create a page somewhere about something and cite it as an authority? Sam Tomato (talk) 05:50, 12 November 2016 (UTC)
thread_title:  Authorities 

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thread_title:  External links modified 

message: Some experts maintain that the ERD is a graphical tool to visualize a conceptual model (which is by the way a different thing from the conceptual schema). A conceptual model is supposed to represent the business world (the universe of discourse or domain of interest that the model is supposed to represent) and such constructs like "keys" or "indices" or "privileges", etc. which are the peculiarities of the database model do not belong in the conceptual model and by extension in the ERD which merely visualizes the conceptual model. Primary keys are relevant to the Logical Model (which broadly translates the conceptual model in terms of a given database model (often relational). Simply put, real world entities do not have a "key". Tables do.
Ehsanamini (talk) 07:42, 27 September 2019 (UTC)
thread_title:  Primarky Keys 

message: To be your lover forever❤️ 41.116.177.176 (talk) 10:41, 17 April 2022 (UTC)
thread_title:  To be in the relationship for least 

message: This article mixes model and diagram in a very confusing way. Confusing for both readers as authors. It starts off rather well in the introduction defining three different levels of model or the three-schema_approach and than leaves that and jumps right into different diagramms and loses track about which is what pretty quickly. For me diagrams are tools to describe a model. 
I realize that there are quite some opinions floating around here but this article as it is now is not very useful for students or experts alike. 
On thing that could help is to call it Entity Relationship Diagram that describe a set of possible, practical notations and tools to describe a relational database schema and leave the conceptual model description out and move it a more high level articale comparing hierarchical, network and relation databases models.
Theking2 (talk) 14:21, 26 March 2024 (UTC)
thread_title:  Distinguish between model and diagram