7.8. Mapping of the AUGMENTS clause
The AUGMENTS clause, which must not be present unless the object
corresponds to a conceptual row, is an alternative to the INDEX
clause. Every object corresponding to a conceptual row has either an
INDEX clause or an AUGMENTS clause.
If an object corresponding to a conceptual row has an INDEX clause,
that row is termed a base conceptual row; alternatively, if the
object has an AUGMENTS clause, the row is said to be a conceptual row
augmentation, where the AUGMENTS clause names the object
corresponding to the base conceptual row which is augmented by this
conceptual row augmentation. (Thus, a conceptual row augmentation
cannot itself be augmented.) Instances of subordinate columnar
objects of a conceptual row augmentation are identified according to
the INDEX clause of the base conceptual row corresponding to the
object named in the AUGMENTS clause. Further, instances of
subordinate columnar objects of a conceptual row augmentation exist
according to the same semantics as instances of subordinate columnar
objects of the base conceptual row being augmented. As such, note
that creation of a base conceptual row implies the correspondent
creation of any conceptual row augmentations.
For example, a MIB designer might wish to define additional columns
in an "enterprise-specific" MIB which logically extend a conceptual
row in a "standard" MIB. The "standard" MIB definition of the
conceptual row would include the INDEX clause and the "enterprise-
specific" MIB would contain the definition of a conceptual row using
the AUGMENTS clause. On the other hand, it would be incorrect to use
the AUGMENTS clause for the relationship between RFC 1573's ifTable
and the many media-specific MIBs which extend it for specific media
(e.g., the dot3Table in RFC 1650), since not all interfaces are of
the same media.
Note that a base conceptual row may be augmented by multiple
conceptual row augmentations.