Logical database structures: Which of the following is not recognized as a standard logical data model?

Introduction / Context:
Logical data models describe how data is conceptually organized and related, independent of physical storage. Classic models include hierarchical (tree), network (CODASYL), and relational models. This question asks you to spot the odd term out.

Given Data / Assumptions:

• Tree, network, and relational are well-established logical models.
• ‘‘Chain’’ is not a standard logical model in database theory.
• Terminology should be historically and academically grounded.

Concept / Approach:
Evaluate each option for its presence in database literature. Tree, network, and relational appear consistently in textbooks and standards. ‘‘Chain’’ lacks definition as a logical model and does not denote a widely accepted schema organization.

Step-by-Step Solution:

Verification / Alternative check:
Relational dominance in practice and the historical presence of hierarchical and network models confirm the standard trio; ‘‘Chain’’ does not appear as a recognized model.

Why Other Options Are Wrong:

• Tree, relational, network: all canonical logical models.
• All of the above: false because three are valid logical models.

Common Pitfalls:
Confusing physical data chains or linked lists with an abstract database model.

Final Answer:
Chain model