IPA IP 2021 Question 70
A question IPA Japan published in 令和3年度 ITパスポート試験 公開問題 問70, translated into English. ITPEC is based on the same exams.
Same question on ITPEC: Apr 2026 Q28 +1 more
When conditions (i) through (iv) are all fulfilled, which of the following is the E-R diagram that indicates the relationship between publishing companies, authors, and books? Here, the notation for the E-R diagram is as below.
[Notation]
This indicates that A and B have a one-to-many relationship.
Explanation
Publishing Company → Author → Book — both relationships are one-to-many, with the arrowhead on the "many" side.
In the notation, A → B means one A relates to many B, so each arrow points from the "one" side to the "many" side.
- •Publishing company and author: a company contracts with many authors (i), and an author with only one company (ii). One company, many authors: Publishing Company → Author
- •Author and book: an author writes many books (iii), and a book is written by one author (iv). One author, many books: Author → Book
Answer (a)
Why not others:
- •(b) — Book → Author would mean one book has many authors, against (iv)
- •(c) — Author → Publishing Company would mean one author contracts with many companies, against (ii)
- •(d) — reverses both relationships
Key rule: Settle each pair of entities on its own: ask "how many of B for one A?" and "how many of A for one B?", then point the arrow at the side that is "many".
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This question comes from the past questions IPA Japan publishes, translated into English by ITPEC Practice. ITPEC Practice is an independent study tool and is not affiliated with IPA or ITPEC. See the original paper (PDF) or Report an issue.