As per Relevance of the word experimental, we have this rfc below:

---

Network Working Group G.
Request for Comments: 1804 AIC
Category: Experimental P.
Hughes Software
S.
Indian Institute of Technology,
T.
University of
June 1995


Schema Publishing in X.500

Status of this

This memo defines an Experimental Protocol for the
community. This memo does not specify an Internet standard of
kind. Discussion and suggestions for improvement are requested
Distribution of this memo is unlimited



The X.500 directory provides a powerful mechanism for storing
retrieving information about objects of interest. To interpret
information stored in the directory, the schema must be known to
the components of the directory. Presently, there are no means
than ftp to distribute schema information across the Internet.
is proving to be a severe constraint as the Directory is growing
This document presents a solution to the schema distribution
using the existing mechanisms of the directory. A naming scheme
naming schema objects and a meta-schema for storing schema objects
presented. The procedures for fetching unknown schema from
directory at runtime are described

Table of

1. Introduction 2
2. Schema Management 2
3. Storage of Schema Information in the Directory 3
4. Retrieval of Schema from the Directory 5
5. The Meta-Schema 6
6. References 9
7. Security Considerations 9
8. Authors' Addresses 10







Mansfield, et al Experimental [Page 1]

RFC 1804 Schema Publishing in X.500 Directory June 1995


1.

The X.500 Directory [1] is now used for a wide range of
from name/address lookup to network management, from
information to bibliographic information services. This
is distributed and managed across a network of many autonomous sites
In order to interpret the information stored in the directory,
components of the directory must have knowledge about the
and representation (schema) of the information held within
directory

The distributed nature of the network and the relatively slow
of standardization have given rise to the challenging task of
accessible the information about the schema rules themselves.
mechanism for making the schema accessible to the
components of the directory is urgently required

The 1993 X.500 Directory Standard [2] has attempted to address
problem of schema management and distribution. The 1993
does provide the means for storing and retrieving schema
in the directory. However, the resolution of unknown OIDs
require both the DUA and the DSA to be compliant with [2].

In this document we propose a solution using the existing
of the directory [1] itself. We present a naming scheme for
schema objects and a meta-schema for storing schema objects in
directory. The proposal allows the algorithmic resolution of
objects in the directory and in the absence of 1993 X.500
Standard implementations provides an interim solution to the
publishing problem

2. Schema

The storage and retrieval mechanism provided by the directory
powerful and flexible. However, the key to the directory is
knowledge of the schema rules defined for the objects represented
the directory. To facilitate the diffusion of this
appropriate schema management mechanisms need to be designed.
management involves

o Storage of schema information in the
o Algorithmic access to and retrieval of schema
in the
o Definition of rules for schema
o Propagation of schema information from one component of
directory to other components of





Mansfield, et al Experimental [Page 2]

RFC 1804 Schema Publishing in X.500 Directory June 1995


In this document we concentrate on the aspect of
access/retrieval from the directory. Since schema objects are
and employed, the modification , addition and deletion of
objects can be carried out using existing directory mechanisms.
the operational issue of synchronizing the schema with the DIB
require further attention. Similarly the issue of schema
requires further work and is outside the scope of this document.
strategy proposed in this document has a very simple and
approach. No added DAP/DSP functionality is envisaged. At the
time by using the directory's distributed framework
problems are avoided. In essence, it allows the distributed
of schema objects and proposes a naming scheme which
algorithmic schema retrieval. Of course, on the down side, more
one directory read operation may be required to retrieve
information about an object and its attributes, as objects
attributes are stored as separate entries in the directory

As schema information of all objects in a naming context are
below the root entry of that naming context, the same DSA will
able to supply the schema information stored in that DSA. Thus
is no need to contact another DSA for resolving the schema of
object stored in the local DSA

3. Storage of Schema Information in the

The schema information may be stored and distributed using
external to the X.500 directory standard [5]. This document
storing schema information in the directory. It has the
advantages

o The components of the directory can access the
information using the standard directory protocols

o The nature of the directory naturally allows the
to be distributed. Schema used locally can be kept in
local DSA itself whereas schema for general objects
person, organization etc can be made available to
components of the directory by publishing it

In the operational model, the schema information in the directory
expected to complement the schema information held in
repositories









Mansfield, et al Experimental [Page 3]

RFC 1804 Schema Publishing in X.500 Directory June 1995


3.1 Naming Scheme for the

The schema information is stored in a distributed manner. We
a model in which each naming context stores the schema relevant
it



\
\
+-------------\----------------------+
| C=IN DSA-1 |
| / \ |
| / \ |
| / \ |
| / \ |
| / cn=subschema |
| / / / | \ \ \ |
| / / / | \ \ \ |
| / oid= oid= |
+--/---------------------------------+
/
+----------------------/----------------------+
| o=IIT, Madras DSA-2 |
| / \ |
| / \ |
| / \ |
| / \ |
| ou=CSE cn=subschema |
| / \ / /| \ \ \ |
| / \ / / | \ \ \ |
|ipni=spark cn=Rajeev oid=ipni oid= |
+---------------------------------------------+

Figure 1: DIT with schema


To store the schema information, an object called subschema object
defined. This object can come anywhere in the Directory
Tree (DIT). The subschema is defined as a subclass of Top.
subschema entry is stored below the root entry of a naming context
The root entry of a naming context must contain a subschema subentry
named {CN= Subschema}. This standard naming methodology is
so that the components of the directory can easily
algorithmically locate the schema entries. All schema
relevant to that naming context is stored below the subschema entry
Children of the subschema entry store information about objects
attribute types, attribute syntaxes or matching rules. The



Mansfield, et al Experimental [Page 4]

RFC 1804 Schema Publishing in X.500 Directory June 1995


structure for storing schema information is shown in Figure 1.
Schema for these objects are given in section 5.

4. Retrieval of Schema from the

When an unknown object is encountered by any component of
during a directory operation, it proceeds the following way
resolve the schema

The RDN component at the leaf-end of the name of the object
schema is to be resolved is replaced by the RDNs "oid=<
identifier of the new object>, CN=subschema" and a read request
initiated for the newly formed name. If the entry is not found,
RDN components from the leaf-end of the name of the object
replaced by the RDNs "oid=