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OsidObjects are consumable interfaces which provide a view into a provider-owned entity. An OSID Provider may or may not provide direct administrative management of the entity. All or part of an OsidObject may be pulled from a data store, the result of data transformation, a representation of a different OsidObject, or completely made up. An OsidObject is an interface that does not reveal anything about underlying data.
In the case of a null value in a database, it is the responsibility of the OSID Provider to determine the value of a return from a mandatory method. In the OSID world, OSID Consumers get no hint from an OsidObject that a null value exists any more than OSID Consumers can understand that the OSID Provider is using a database.
So, what to do when there is no data to satisfy a mandatory method.