search with negation of undefined objectClass returns nothing

["Charlie H" <askldapquestion@hotmail.com>]

Hello,

I?ve been working on a conversion of a directory to OpenLDAP.  I stumbled 
upon some search results that I could not explain.

One of our programs searches for LDAP entries with a negation of certain 
object classes, so that extraneous entries are ignored.  In OpenLDAP, if the 
passed objectClass is not defined (as a valid objectClass in the schema), it 
returns back nothing every time.

For example, as expected, this returns back entries without the surname xx:

 $ ldapsearch -xb "o=OrgName,c=US" '(!(sn=xx))'

And this will return back entries that do not have the groupOfNames 
objectClass:

 $ ldapsearch -xb "o=OrgName,c=US" '(!(objectClass=groupOfNames))'

But the negation of an undefined objectClass returns nothing (without any 
error):

 $ ldapsearch -xb "o=OrgName,c=US" '(!(objectClass=xx))'

On another LDAP system (iPlanet), the last query above returns back all 
entries.  Does OpenLDAP by design throw out the search for an objectClass 
value that is not defined?  Could this be a configuration issue?

Many thanks for all of your efforts in this project!  --charlie h.

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