Rationale for compulsory objectClass top in RFC2256 5.1

[Christian Kratzer <ck-lists@cksoft.de>]

Hi,

I have always wondered about directories that have included objectClass top
in every entry even though practically any usefull objectClass inherits
from top eventually.

Apparantly RFC2256 5.1 requests this:

 5.1. objectClass

   The values of the objectClass attribute describe the kind of object
   which an entry represents.  The objectClass attribute is present in
   every entry, with at least two values.  One of the values is either
   "top" or "alias".

    ( 2.5.4.0 NAME 'objectClass' EQUALITY objectIdentifierMatch
      SYNTAX 1.3.6.1.4.1.1466.115.121.1.38 )

It seems RFC4512 addresses the matter in:


  A.3.  Changes to RFC 2256

   This document incorporates Sections 5.1, 5.2, 7.1, and 7.2 of RFC
   2256.

   Section 5.1 of RFC 2256 provided the definition of the 'objectClass'
   attribute type.  This was integrated into Section 2.4.1 of this
   document.  The statement "One of the values is either 'top' or
   'alias'" was replaced with statement that one of the values is 'top'
   as entries belonging to 'alias' also belong to 'top'.

So this means objectClass top is still compulsory in every entry as in:

      dn: cn=bar,dc=example,dc=com
      objectClass: top
      objectClass: alias
      objectClass: extensibleObject

which means somehting like the following would be illegal:

      dn: cn=Hugo,dc=example,dc=com
      objectClass: person

Can anybody comment on the rationale why this is needed ?

I somehow completely fail to see the purpose.

Greetings
Christian

--
Christian Kratzer                      CK Software GmbH
Email:   ck@cksoft.de                  Wildberger Weg 24/2
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Web:     http://www.cksoft.de/         Geschaeftsfuehrer: Christian Kratzer