How to represent a one-to-many relationship with total participation on the one side in an E-R diagram

Question

Suppose there is an entity set representing people and an entity set representing books, and they are in a relationship about authoring. Suppose that every person must have authored at least one book (total participation) and every book must have been authored by at most one person. How would one describe this relationship in terms of an E-R model? Assume that Person entity set is on the left, Book on the right, and Authored relationship set in the middle.

It seems to me that if one uses a double line on the Person side that one cannot use an arrow on the Person side to represent the "one" cardinality restriction (for any given book, at most one person authors the book).

The follwoing is close to what I think captures the relationship, but it seems not enough:

Person ============ Authored ----------- Book

but does not restrict books to have at most one author. Also, the following alternative:

Person <----------- Authored ----------- Book

does not indicate total participation of people in Person.

Answer 1

The answer to this question depends on the ERD notation you are using.

According to your narrative:

• The participation of Person to the Authored relationship is total.
• The participation of Book to the Authored relationship is partial. (this model allows for unknown authors, but at the same time prohibits collective books which are a reality)

The answer depends on the notation. In the classical Chen ERD notation your first approach is correct (authored would be enclosed in a diamond). You just have to indicate the maximum cardinality:

+--------+      1                     N    +------+
| Person |============ Authored -----------| Book |
+--------+                                 +------+

In my view, this is confusing, since the participation (minimum cardinality) is on the opposite side of the maximum cardinality. Note that in his original articles, Peter Chen does not use total/partial notation.

In the Crow's foot notation, you'd use

                       Authored
Person -|o--------------------------------|< Book

If you use another notation, you need to clarify which one or ask the person who has taught you this notation.