subschema clarifications (Was: I-D ACTION:draft-ietf-ldapbis-models-01.txt)

["Kurt D. Zeilenga" <Kurt@OpenLDAP.org>]

At 07:47 AM 2002-05-30, Kurt D. Zeilenga wrote:
>Summary of technical changes made:
>  - clarified schema publishing / discovery;

A little elaboration...

This revision includes clarifications aimed at resolving a
couple of subschema discovery issues.

Over the years, a number of questions have been raised
regarding how clients determine that a server supports
capabilities associated with elements of schema, in
particular, operational attributes.  For example, how
does a client determine whether a server supports
DIT Content Rules.

I've taken statements in Section 4.1.4 of RFC 2251 that
the attributeTypes attribute is used to indicate "support"
for an attribute type.  In -00 revision of the I-D, a
server indicated support for a number of capabilities
(such as DIT Content Rules) by publishing the definition(s)
of attribute type(s) associated with the capability.

But for this to be a clear indication of support, it is
necessary to disallow servers which don't support the feature
from publishing the defintions associated with that feature.
Hence, the -01 revision includes the statement:

   A server SHALL only publish schema definitions for
   elements it supports.

Without this, the discovery mechanism would be fundamentally
broken.

However, the added statement can be viewed as inconsistent
with other statements made in existing "core" technical
specification.  So, it might be appropriate to clarify
that the subschema mechanism is not capability discovery
mechanism.  If so, do we need one or can we live with
trial and error discovery mechanism?  (Personally, I can
live with trail and error, that's what most clients will
do anyways.)