In ODMG's Object Definition Language (ODL), if all possible values of an attribute are known in advance, can those values be explicitly enumerated in the type declaration (for example, by using an enumeration to restrict the attribute domain)?

Introduction / Context:
Object database standards such as the ODMG model define ODL (Object Definition Language) to declare classes (interfaces), attributes, relationships, keys, and extents. A frequent design task is to constrain an attribute to a small, closed list of allowed values. This question checks whether ODL supports that pattern by allowing enumeration of all valid values directly in the type system.

Given Data / Assumptions:

• We are using ODMG-style ODL to model persistent classes and their attributes.
• The attribute in question has a finite, known set of values (for example, status ∈ {NEW, ACTIVE, SUSPENDED}).
• We want a schema-level constraint rather than only runtime checks.

Concept / Approach:
ODL supports literal types and type declarations, including enumerations. When the domain is closed and known, an enumeration provides a compact, precise way to express the allowed values. This improves clarity and minimizes invalid data by preventing values outside the list from being assigned.

Step-by-Step Solution:
Decide the attribute requires a closed set of values.Define an enumeration type in the ODL schema to list those values.Declare the attribute using that enumeration type.Persist and query objects; the type system ensures only enumerated values are stored.Document semantics for each enumerated constant to aid application developers.

Verification / Alternative check:
Compare the enumeration approach against using a free-form string. With enumeration, tools can catch invalid assignments during compilation or schema validation; without it, mistakes become runtime data-quality issues.

Why Other Options Are Wrong:
Restricting to numerics only (option c) is incorrect; enumerations cover many literal kinds. Keys-only (option d) misunderstands keys versus attribute domains. Transient-only (option e) is unrelated; enumerations apply equally to persistent classes. Saying ODL cannot restrict an attribute (option b) ignores enumeration support.

Common Pitfalls:
Overusing enumerations for values that actually change over time (better modeled as reference objects); failing to version enumerations when business states evolve; mixing display labels with internal enumeration constants without a mapping layer.

Final Answer:
Applies — ODL allows enumerating all permissible values for an attribute