Some attribute types are used as references to other object instances. These attribute values are the linked object’s identifier (OID). They are not modifiable using OData services. Sort, selection, and filtering are unsupported for these attribute types. Attribute types include multi-object, iterated multi-object, discussion, object reference, version reference, and user list.

The OID can be used by a client with some REST services to retrieve instance data or perform some operations. See REST services documentation for more details.