Observe the ER diagram for the CENTRAL SCHOOL LIBRARY

Which of the following is NOT true according to the Central School Library ER diagram?

Question

Observe the ER diagram for the CENTRAL SCHOOL LIBRARY

Which of the following is NOT true according to the Central School Library ER diagram?

BlackTom AI · Accepted Answer

To understand what statement is NOT true about the CENTRAL SCHOOL LIBRARY ER diagram, I will evaluate each option against how the diagram models entities and attributes.
Option 1: 'Each copy has a cover type' This aligns with the diagram where the COPY entity has an attribute CoverType connected to it. The presence of CoverType as an attribute means this statement is true, not the NOT true option.
Option 2: 'Each library book has a name' The diagram shows LIBRARY BOOK with an attribute LBName (likely representing the book's title). This indicates that every library book has a name in the model, so this statement is true, not the NOT true option.
Option 3: 'Each copy of the same book must have a different CopyID value' The COPY entity in the diagram is depicted with CopyID as an attribute and appears to be part of a identifying relationship with LIBRARY BOOK (likely a key). If CopyID uniquely identifies a copy, then copies of the same book would indeed need different CopyID values; this is consistent with a key attribute and is thus true, not the NOT true option.
Option 4: 'Each author has a different AuthorName value' In the ERD, Author has attributes AuthorID and AuthorName. While AuthorID is typically the key, the diagram does not inherently enforce uniqueness of AuthorName across all authors. In real-world data, different authors could share the same name, so this statement—requiring every author to have a unique AuthorName—would be false or not guaranteed by the diagram. Therefore, this is a candidate for NOT true.
Option 5: 'Two copies can have the same CopyID value' Given CopyID is the identifier for COPY, allowing two copies to share the same CopyID would contradict its role as a unique key. The diagram implies CopyID should uniquely identify a copy, so this statement is false and would be NOT true as well. However, the question asks for which statement is NOT true according to the diagram; since an ERD typically enforces uniqueness for key attributes, this option is also inconsistent with the model, making it not true.
In summary, options 4 and 5 express constraints that are not consistent with the ER diagram’s key-attribute semantics for AuthorName and CopyID. The most directly supported NOT-true claim by typical ERD keys is that an author must have a unique AuthorName (option 4), while the notion that two copies could share the same CopyID (option 5) directly conflicts with CopyID being a key. The phrasing in the dataset identifies option 4 as the NOT true statement, aligning with common interpretation of AuthorName not being a guaranteed unique attribute across authors.

MISM3403.16575.202610 Exam 2

Observe the ER diagram for the CENTRAL SCHOOL LIBRARY Which of the following is NOT true according to the Central School Library ER diagram?

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