RFC 1026 (rfc1026) - Page 2 of 4

Addendum to RFC 987: (Mapping between X

RFC 1026                                                  September 1987


There are three places where an order must be specified:

   1)   On the text encoding (std-orname) of P1.ORName as used in the
        local-part of an RFC-822 address, the most significant component
        must be on the RHS.  This applies only to those components which
        may have multiple values (Organisational Unit, and Domain
        Defined Attributes).  Other attributes may be presented in any
        order. Note that in dmn-orname specified in Appendix F, this
        ordering is already implied by the current ordering
        requirements.

   2)   For the Organisational Units (OU) in P1.ORName, the first OU in
        the SEQUENCE is the most signicicant.  This follows the
        "natural" hierarchy of the specification of P1.ORName, where the
        most significant components are defined first.

   3)   For the Domain Defined Attributes in P1.ORName, the First Domain
        Defined Attribute in the SEQUENCE is the most significant.

   Note that although the ordering defined in 2) and 3) is mandatory for
   this mapping, there are NO implications on ordering significance
   within X.400.

   3.  Extensions To Deal with Omitted Components

   Implementation of RFC-987 has proved to be a little inflexible for
   some naming strategies.  In particular, there are some difficulties
   where Organisation or PRMD is omitted:

   The following sentence of RFC-987 should be removed: 4.2.1 (Page 27):
   "If one of the hierarchical components is omitted ....  tuple).".

   The strategy proposed is to introduce the concept of explicit missing
   components to the symmetrical mapping described in 4.2.1.
   Essentially, a domain may be associated with an omitted attribute in
   conjuction with several present ones.  When performing the
   algorithmic insertion of components lower in the hierarchy, the
   omitted value should be skipped.  For example, if "GMD.DFN" is
   associated with "C=DE", "ADMD=DBP", "PRMD=GMD", and omitted
   organisation, then "ZI.GMD.DFN" is mapped with "C=DE", "ADMD=DBP",
   "PRMD=GMD", "OU=ZI".  It should be noted that attributes may have
   null values, and that this is treated separately from omitted
   attributes (whilst it would be bad practice to treat these two cases
   differently, they must be allowed for in practice).










Kille