There is no explicit type oid for object identifiers. Nested records are not supported. Position selectors can only be applied to variables and not to list and record constructors directly. Formulas Formulas are not declarative. Their compilation as well as their evaluation depends on the order of their literals.
External names have to be typed to an object class before they can be used.
They must however be unique with respect to the entire database. There is no difference between persistent and temporary objects. Referential integrity is not enforced after object deletion. Query events are not registered and thus not recognized as events. The command savepoint is not supported.