Which logical data model establishes a strict top-to-bottom (tree) relationship where each child has exactly one parent but a parent may have multiple children?
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AHierarchical schema
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BNetwork schema
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CRelational schema
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DAll of the above
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ENone of the above
Answer
Correct Answer: Hierarchical schema
Explanation
Introduction / Context:Choosing a data model affects how relationships are expressed and constrained. The hierarchical model organizes records into a tree, enforcing a one-to-many parent–child structure that simplifies certain traversals but restricts lateral relationships.
Given Data / Assumptions:
- Each child record must have exactly one parent.
- A parent may have zero or more children.
- No many-to-many or multi-parent relationships are allowed.
Concept / Approach:
Hierarchical schemas (e.g., IBM IMS) represent data as rooted trees. In contrast, network schemas allow many-to-many via owner/member sets, and relational schemas express relationships flexibly with keys and join tables without enforcing a single-parent rule. Therefore, the described top-to-bottom relationship is characteristic of a hierarchical schema.
Step-by-Step Solution:
Match ‘‘single parent per child’’ to a tree structure.Associate tree structures with hierarchical databases.Exclude network (many-to-many) and relational (general keys/joins) models.Select ‘‘Hierarchical schema’’.Verification / Alternative check:
Legacy mainframe systems and textbooks consistently define hierarchical models by a strict parent–child tree with one parent per child node.
Why Other Options Are Wrong:
Network schema: Supports multiple owners; not a strict tree.
Relational schema: Uses tables and keys; no enforced single parent relationship.
All/None: Do not match the precise description.
Common Pitfalls:
Confusing logical models (hierarchical vs. network) when converting legacy systems to relational schemas.
Final Answer:
Hierarchical schema