Derived attribute meaning: Is a derived attribute one whose value can be calculated from other data (including attributes in related entities or relationships)?

Introduction / Context:
Derived attributes help reduce redundancy and keep stored data minimal by computing values from existing data when needed. This question evaluates whether a derived attribute can be computed from related entities or relationship data, not only from attributes within the same entity.

Given Data / Assumptions:

• An ER model includes entities, attributes, and relationships.
• Derived attributes are not persistently stored by default; instead, they are computed.
• “Related relationship” refers to data reachable via a relationship (e.g., line items, rates, or constraints).

Concept / Approach:
A derived attribute is any attribute whose value can be calculated from other data in the model. This includes values based on attributes of the same entity (e.g., age from date_of_birth and today), on related entities (e.g., total_order_value from order_line amounts), or on relationship-level facts (e.g., price_at_time on a participation that stores negotiated price). The key property is computability, not storage location.

Step-by-Step Solution:
Identify the target attribute (e.g., customer_age).Locate source data that deterministically yields the value (date_of_birth and current_date).If the source resides in a related entity or the relationship, ensure a well-defined join/association exists.Express the derivation rule clearly for implementation (view, computed column, or application logic).

Verification / Alternative check:
Prototype a query or view showing the computed value. If the same value can be reproduced consistently from source data, the attribute is legitimately derived.

Why Other Options Are Wrong:
Restricting derivations to the same entity ignores common cross-entity calculations. Claiming derivations exist only in dimensional modeling is false; derivations are fundamental to ER modeling as well.

Common Pitfalls:
Persisting derived data without governance leads to inconsistencies. Not documenting derivation logic creates ambiguity.

Final Answer:
Correct