How to express a “some of which are” and “not all are” relationship with enhanced entity-relationship diagrams

The key to understand this case is at the ninth page from Doc-A:

"product" and "customer" are entity types, and "shipped to" is a relationship... the verb "ship" is then converted to a gerund... in other words, the relationship... has been converted into the entity type "shipping"

Hence, the final third form will have "shipped to" converted to an entity by itself, "shipping".

This is necessary because "Shipped to" is a MANY-TO-MANY relationship (although to myself Chen's text is not clear on this).

But, your example does not relate - the relationship "Identified by" is an ONE-TO-MANY (a card belongs to ONE customer / a customer have ONE OR MORE cards issued).

Hence, the model would have the relationship between "Bank" and "Bank card" identified by TWO verbs.

Or, making the model stronger, to register several authentication events, one may turn "Authenticated by" into a entity by itself, "Authenticating" (to register event date, data shared, etc.).

I am not sure if this is the right place to pose such questions. But here some remarks and questions anyway. They are too long for a comment.

• I don't understand the word representant. I did not find it at http://dict.leo.org/. Dou you mean representative?

• With telephones you mean phone numbers and with emails you mean email adresses?

• Why is telephone a weak entity? What is its identifying entity? For me it is not a weak entity. A phone extension may be a weak entity. The same holds for email and address.

• can a representant have more then one address? This is not excluded by the text but it is excluded by the ER diagtram.

• Why do you name some entities as singular and some as plural? I think a consisten notation will be more clear.

• Why do one need a reading direction? What is the difference if one reads the diagram from bottom to top? I see no difference.

• "if a representant is removed it must be saved in a list" That does not describe any relationships between a removed representant and the remaining entities. "it must be saved" is a term of computer programming and not of the business domain. It is not clear to me what you want but using an attribute to a relation may be not the appropriate solution. From your drawing I conclude a telephone is assigned to a representant. If the representant is removed the removed representant has a telephone too? If yes then this telephone cannot be used by then new representant for this address because a telephone has only one representant assigned.