Note: Reader mail (rm) posts are my exchanges with readers that raise fundamental issues. I may improve language for clarity and amplify with notes for the benefit of readers.

I've written more than once about Chen's E/RM (see references) and recently a reader emailed me a reaction to one of these writings, offering E/RM as evidence that properties were not necessary in conceptual modeling -- everything could be expressed with just entities and relationships. That is, of course, incorrect, but I was working at the time on my latest series of posts on Relationships and the RDM, which was going to address that issue too and I intended to refer him to it. But knowing that David McGoveran knew Chen in the 80s, I asked him if he had any comments. He thought that something broader and more forceful regarding Chen's work was in order and suggested some text. We had some discussion on the subject and decided that I will post my reply (ON PROPERTIES IN CONCEPTUAL MODELING) and publish his reply to the reader later, which I do below.

Note: Reader mail (rm) posts are exchanges with my readers that raise fundamental issues. I may improve language for clarity and amplify with Ed. Notes for the benefit of readers.

“Your post Understanding Conceptual vs. Data Modeling Part 1: Data Model - The RDM Is, the E/RM Isn't is well done. However, concepts and relationships can be perceived and modeled without formulating or specifying properties. Chen did that in his ER diagrams. And informally, everyone does it as a mental model every day. I suppose anyone can define conceptual modeling however they wish to.  But at its minimum and most abstract, which is what conceptual modelling is usually understood to be, it can be done without formulating or specifying properties.” --GR

“Over the past decade, there have been a number of DBMSs introduced (typically labeled as NoSQL) which utilize a network or hierarchical data model. MongoDB and Cassandra come immediately to mind as examples. Some such systems support networks through the concepts of "links" and some support hierarchical data using a nested data model often utilizing JSON. In my opinion, these systems have not internalized lessons from history.

“At the SIGFIDET (now SIGMOD) annual conference in 1974, there was a "Great Debate" over the merits of the relational model versus the network and hierarchical models ... Basically, the argument was about which model [relational or network] was a better fit for structured data (as opposed to documents, e-mails, etc.) and boiled down to two questions:

Question 1: Are high-level data sublanguages a good idea?
Question 2: Are tables the best data structure or should one use a network or hierarchy?”

“The last 45 years have definitely affirmed Codd’s position on both issues ... The conclusion from the 1970s was that the relational model provides superior data independence, compared to the network and hierarchical [graph] models. Forty-five years later, this conclusion is still true. If you want to insulate yourself from the changes that business conditions dictate, use a relational DBMS. If you want the successor to the successor to your job to thank you for your wise decision, use a relational model.”

"Entity-Relationship Model"

“One of the first formal attempts at a framework for Data Modeling was the Entity-Relationship data model paradigm proposed [in 1976] by Peter Chen. Notice that in the original Chen-style, the attributes are somewhat independent and the relationships between entities are named and carry cardinalities ("how many" participants in each end of the relationship) ... Attributes are related to their "owner" entity" in what other people called "functional dependencies".”

“The term data model is used in two distinct but closely related senses. Sometimes it refers to an abstract formalization of the objects and relationships found in a particular application domain, for example the customers, products, and orders found in a manufacturing organization. At other times it refers to a set of concepts used in defining such formalizations: for example concepts such as entities, attributes, relations, or tables. So the "data model" of a banking application may be defined using the entity-relationship "data model". This article uses the term in both senses.”

--Data Model, Wikipedia

What a True Data Model Is

“The E/RM is not a data model as formally defined by Codd: no explicit structural component except sets classified in various ways, no explicit manipulative component except implied set operations, and very limited integrity (keys).”

--David McGoveran

“[It] is not even clear that the E/R "model" is truly a data model at all, at least in the sense in which we have been using that term in this book so far (i.e., as a formal system involving structural, integrity, and manipulative aspects). Certainly the term "E/R modeling" is usually taken to mean the process of deciding the structure (only) of the database, although [it does deal with] certain integrity aspects also, mostly having to do with keys ... However, a charitable reading of [Chen's original E/RM paper] would suggest that the E/R model is indeed a data model, but one that is essentially just a thin layer on top of the relational model (it is certainly not a candidate for replacing the relational model, as some have suggested).”[2]

“E/RM is a data model -- So says Date, Chen, etc. So says the majority of current industry experts ... With very strong references to Codd (who he worked with), Date elegantly explains the differences between RM and E/RM -- but clearly believes both are data models (even allowing for the charitable comment). If we take a RDB as the ultimate target implementation of data, and an E/RM (or extended) can correctly design all the artifacts that are implemented, this means it is modeling the data. Granted, an E/RM does not explicitly model some of the non-structural aspects of the original Codd definition.”

“Out of interest, is there a common Relational Modeling tool, that is not also an E/RM tool and models the full Codd definition? There are also several other methods of modeling data -- E/RM is more a mechanism to represent the data. If E/RMs are used by IT professionals across the world to direct the design and build of the majority of applications guided by standard methodologies, is the view of this argument that these were all build wrongly? Regardless of success? Is the inferred conclusion that only the RM models data, and ERM, [or] any other techniques do not? [If so] that is a little limiting.”

Objects, Properties, and Ontological Commitment