Are attributes mandatory in Chen's ERD diagram?

Question

Is it mandatory to add the attribute symbols in an ERD diagram when using Chen's notation?

I'm asking because in my current ERD there are already so many tables and relations that an A3 paper size is needed to print it out. Adding all the attribute symbols would make it even larger and less readable. I therefore wonder if it is an obligation or if I could leave them out. And if it is mandatory, how could I maintain my diagram readable?

Answer 1

It is not mandatory in Chen's notation to show the attributes.

In his seminal articles (for example here), Chen uses several diagrams with only entities and their relationships. This forms what he calls the "upper conceptual domain", i.e. the big picture. The details of the attributes could be documented elsewhere, for example in additional diagrams that "zoom" one or a few entities, or in a tabular data dictionary that describes the content of each entity.

You may also enrich this approach by showing in addition to the entities and relationships, the most relevant attributes: all the key attributes, and a few additional attributes that allow the reader to imagine the kind of information that the entity represents. The attributes belong to the "lower conceptual model" (Chen's terminology).

If you would want to shall all the attributes, and if the separate dictionary is not desirable for you, you could break the model down into several smaller models each having all the attributes for their entities and relationships. Some entities would appear in several diagrams to allow to make the link between them. The attribute details would then be detailed in only one of the diagrams and hidden in the others.