Classes: Referential Integrity

• OIDs can refer to an object anywhere in DB

• Objects can be referenced from anywhere in DB

• Insertion or deletion of a reference can never violate referential integrity

• Assume automatically maintained extents

• Deletion of a referenced object, default:

  • Same as SQL-92: disallow deletion from extent

• Methods can enforce other delete semantics

  • Cascading delete, set NULL, or set default

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