According to the ODMG Object Model, are relationships directly supported only as unary (recursive) or binary links between classes, with n-ary associations modeled via intermediate objects rather than native n-ary relationship syntax?

Introduction / Context:
Relationship modeling is central to object databases. The ODMG Object Model and ODL provide a built-in way to declare relationships with optional inverse specifications, enabling bidirectional navigation and referential integrity. This item examines whether ODMG supports only unary (a class related to itself) and binary (between two classes) relationships directly, leaving n-ary associations to be represented via association objects.

Given Data / Assumptions:

• ODMG ODL is used to declare attributes and relationships.
• Unary is a special case of binary where both ends are the same class (recursive relationship).
• No special native ODL syntax exists for relationships among three or more classes in one declaration.

Concept / Approach:
ODL declares relationship members between two classes, typically coupled with an inverse relationship to maintain consistency. When a conceptual model includes an n-ary relationship, standard practice is to introduce an association (link) class that holds the participants; the n-ary association becomes a regular object with binary relationships to each participant.

Step-by-Step Solution:
Identify an n-ary requirement (e.g., Student–Course–Semester).Create an association class (e.g., Enrollment) capturing attributes of the relationship.Declare binary relationships from the association class to each participant with inverses.Use instances of the association class to represent each n-ary link.Navigate via the association object to access all related participants.

Verification / Alternative check:
Review ODL grammar and examples: you will find binary relationship declarations, not direct n-ary constructs. Industry texts show association objects as the idiomatic solution.

Why Other Options Are Wrong:
Option b is incorrect because native n-ary relationship syntax is absent in ODL. Options c, d, and e introduce irrelevant constraints (persistence, key composition, or extents) that do not change the binary nature of ODL relationships.

Common Pitfalls:
Forgetting to declare inverses, causing asymmetric navigation; embedding relationship attributes on a participant class rather than on the association object; attempting to simulate n-ary links with multiple overlapping binaries without a central association, which loses integrity.

Final Answer:
Applies — ODMG directly supports only unary/binary relationships