[This is preliminary documentation and subject to change.]
It is possible to specify an INDEX clause containing an inaccessible "indexobject", a named value referencing an OBJECT-TYPE definition, that refers to a MIB object definition appearing within the conceptual row of the table containing the INDEX clause or another table. In this case, the MIB object definition referred to in the INDEX clause becomes a keyed property of the class definition but is annotated with the CIM property qualifier virtual_key. The virtual_key qualifier specifies that the SNMP providers calculate the value of the property based on the superset of instance information associated with all the accessible MIB object definitions present within the class definition. A class definition must contain at least one property that does not have an associated virtual_key qualifier; failure to specify this property invalidates the class definition.