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From Howard Chu <>
Subject Re: Question about new OC addition to the schema
Date Sat, 12 Dec 2009 23:25:57 GMT
Emmanuel Lecharny wrote:
> Another Q :
> what should we do if we create an OC containing an AT (in MAY or MUST,
> that's irrelevant) which is already present in one of it's parents ?
> Should it be considered as an error ?
No. X.501 is quite clear on this. Section 8.3 "Object Classes"

The specification of an object class identifies whether an attribute is 
mandatory or optional; this specification also
applies to its subclasses. The subclass may be said to inherit the mandatory 
and optional attribute specification of its
superclass. The specification of a subclass may indicate that an optional 
attribute of the superclass is mandatory in the

So it's explicitly allowed for a subclass to turn a parent MAY into a MUST. 
(And by omission, it's not allowed to turn a MUST into a MAY.)

Also, object classes support multiple inheritance. I'm pretty sure you'll find 
many legitimate cases of an attribute appearing in multiple instances in an 
inheritance chain.

   -- Howard Chu
   CTO, Symas Corp. 
   Director, Highland Sun
   Chief Architect, OpenLDAP

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