DMC Data Modeling Fundamentals 2 — Questions and Answers
Question 1: What is a surrogate key?
- A key borrowed from another table
- A system-generated identifier with no business meaning (Correct answer)
- A composite key made of multiple columns
- A natural identifier from the real world
Correct answer: A system-generated identifier with no business meaning
A surrogate key is a system-generated, meaningless identifier — typically an integer sequence — used solely to uniquely identify a row.
Question 2: Which of the following is a characteristic of a natural key?
- It is always numeric
- It derives its value from business attributes that already exist (Correct answer)
- It is generated by the database system
- It never appears in reports
Correct answer: It derives its value from business attributes that already exist
A natural key is derived from existing business data — such as a Social Security number or product barcode — that already has meaning in the real world.
Question 3: What is the key difference between a strong entity and a weak entity?
- Strong entities have more attributes than weak entities
- A weak entity cannot be uniquely identified without referencing its parent entity (Correct answer)
- Strong entities use surrogate keys; weak entities use natural keys
- Weak entities cannot have relationships
Correct answer: A weak entity cannot be uniquely identified without referencing its parent entity
A weak entity depends on a parent (owner) entity for its identification and cannot be uniquely identified by its own attributes alone.
Question 4: What does the term 'optionality' refer to in a data model?
- Whether an attribute can store NULL values
- Whether a relationship participation is mandatory or optional (Correct answer)
- The choice between surrogate and natural keys
- Optional indexes on non-key columns
Correct answer: Whether a relationship participation is mandatory or optional
Optionality describes whether an entity's participation in a relationship is mandatory (must exist) or optional (may or may not exist).
Question 5: Which modeling artifact is used to document the meaning and origin of a single data element across an enterprise?
- Entity-Relationship Diagram
- Conceptual schema
- Data element definition record (Correct answer)
- Physical table script
Correct answer: Data element definition record
A data element definition record captures the business name, definition, data type, source, and steward of a single atomic piece of data.
Question 6: In the context of DMC, what does 'domain' mean when applied to an attribute?
- The network domain hosting the database
- The set of all valid values an attribute can hold (Correct answer)
- The business unit that owns the data
- The geographic region of data storage
Correct answer: The set of all valid values an attribute can hold
A domain is the complete set of allowable values for an attribute, defined by data type, length, format, and business constraints.
DMC Data Modeling Fundamentals 2
What is a surrogate key?