Cardinality and participation: If the minimum and maximum number of instances of an entity in a relationship are both one, what does this indicate about participation?

Introduction / Context:
ER models frequently annotate relationships with minimum and maximum participation. Minimum indicates whether an instance is required to participate (0 = optional, 1 = mandatory). Maximum indicates whether at most one or many related instances are allowed.

Given Data / Assumptions:

• Minimum = 1 means participation is required.
• Maximum = 1 means at most one related instance is allowed.
• We are interpreting these values for a single entity's role in a relationship.

Concept / Approach:
Minimum 1 and maximum 1 together imply that each instance must participate exactly once in the relationship. This is called “mandatory one” participation. It is distinct from “optional one” (min 0, max 1) and “mandatory many” (min 1, max many).

Step-by-Step Solution:

Verification / Alternative check:
Cross-check with ER notations (crow's foot or min–max notation): (1,1) denotes mandatory one.

Why Other Options Are Wrong:

• Optional one: would require minimum 0.
• Mandatory many: would require maximum many.
• Cannot tell: we can tell because both min and max are specified as 1.
• Optional many: would have minimum 0 and maximum many.

Common Pitfalls:
Confusing “one-to-one relationship type” with participation on a single side; min/max are per role and must be read carefully.

Final Answer:
Mandatory one