Network Working Group                                            S. Kille
Request for Comments: 2293                                     Isode Ltd.
Obsoletes: 1837                                                March 1998
Category: Standards Track


       Representing Tables and Subtrees in the X.500 Directory

Status of this Memo

  This document specifies an Internet standards track protocol for the
  Internet community, and requests discussion and suggestions for
  improvements.  Please refer to the current edition of the "Internet
  Official Protocol Standards" (STD 1) for the standardization state
  and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

  Copyright (C) The Internet Society (1998).  All Rights Reserved.

Abstract

  This document defines techniques for representing two types of
  information mapping in the OSI Directory [1].

  1.  Mapping from a key to a value (or set of values), as might
      be done in a table lookup.

  2.  Mapping from a distinguished name to an associated
      value (or values), where the values are not defined by the owner
      of the entry.  This is achieved by use of a directory subtree.

  These techniques were developed for supporting MHS use of Directory
  [2], but are specified separately as they have more general
  applicability.
















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1  Representing Flat Tables

  Before considering specific function, a general purpose technique for
  representing tables in the directory is introduced.  The schema for
  this is given in Figure 1.  A table can be considered as an unordered
  set of key to (single or multiple) value mappings, where the key
  cannot be represented as a global name.  There are four reasons why
  this may occur:

  1.  The object does not have a natural global name.

  2.  The object can only be named effectively in the context of
      being a key to a binding.  In this case, the object will be given
      a natural global name by the table.

  3.  The object has a global name, and the table is being used
      to associate parameters with this object, in cases where they
      cannot be placed in the objects global entry.  Reasons why they
      might not be so placed include:

       o  The object does not have a directory entry

       o  There is no authority to place the parameters in the
          global entry

       o  The parameters are not global --- they only make sense
          in the  context of the table.

  4.  It is desirable to group information together as a
      performance optimization, so that the block of information may be
      widely replicated.

  A table is represented as a single level subtree.  The root of the
  subtree is an entry of object class Table.  This is named with a
  common name descriptive of the table.  The table will be located
  somewhere appropriate to its function.  If a table is private to an
  MTA, it will be below the MTA's entry.  If it is shared by MTA's in
  an organization, it will be located under the organization.

  The generic table entry contains only a description.  All instances
  will be subclassed, and the subclass will define the naming
  attribute.  Two subclasses are defined:









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table OBJECT-CLASS ::= {
   SUBCLASS OF {top}
   MUST CONTAIN {commonName}
   MAY CONTAIN {manager}
   ID oc-table}


tableEntry OBJECT-CLASS ::= {
   SUBCLASS OF {top}
   MAY CONTAIN {description}                                       10
   ID oc-table-entry}

textTableEntry OBJECT-CLASS ::= {
   SUBCLASS OF {tableEntry}
   MUST CONTAIN {textTableKey}
   MAY CONTAIN {textTableValue}
   ID oc-text-table-entry}

textTableKey ATTRIBUTE ::= {
   SUBTYPE OF name                                                 20
   WITH SYNTAX DirectoryString {ub-name}
   ID at-text-table-key}

textTableValue ATTRIBUTE ::= {
   SUBTYPE OF name
   WITH SYNTAX  DirectoryString {ub-description}
   ID at-text-table-value}

distinguishedNameTableEntry OBJECT-CLASS ::= {
   SUBCLASS OF {tableEntry}                                        30
   MUST CONTAIN {distinguishedNameTableKey}
   ID oc-distinguished-name-table-entry}

distinguishedNameTableKey ATTRIBUTE ::= {
   SUBTYPE OF distinguishedName
   ID at-distinguished-name-table-key}

                    Figure 1:  Representing Tables


  1.  TextEntry, which define table entries with text keys,
      which may have single or multiple values of any type.  An
      attribute is defined to allow a text value, to support the
      frequent text key to text value mapping.  Additional values may
      be defined.






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  2.  DistinguishedNameEntry.  This is used for associating
      information with globally defined objects.  This approach should
      be used where the number of objects in the table is small or very
      sparsely spread over the DIT. In other cases where there are many
      objects or the objects are tightly clustered in the DIT, the
      subtree approach defined in Section 2 will be preferable.  No
      value attributes are defined for this type of entry.  An
      application of this will make appropriate subtyping to define the
      needed values.

  This is best illustrated by example.  Consider the MTA:

  CN=Bells, OU=Computer Science,
  O=University College London, C=GB

  Suppose that the MTA needs a table mapping from private keys to fully
  qualified domain names (this example is fictitious).  The table might
  be named as:

  CN=domain-nicknames,
  CN=Bells, OU=Computer Science,
  O=University College London, C=GB

  To represent a mapping in this table from "euclid" to
  "bloomsbury.ac.uk", the entry:

  TextTableKey=euclid, CN=domain-nicknames,
  CN=Bells, OU=Computer Science,
  O=University College London, C=GB

  will contain the attribute:

  TextTableValue=bloomsbury.ac.uk

  A second example, showing the use of DistinguishedNameEntry is now
  given.  Consider again the MTA:

  CN=Bells, OU=Computer Science,
  O=University College London, C=GB

  Suppose that the MTA needs a table mapping from MTA Name to bilateral
  agreement information of that MTA. The table might be named as:

  CN=MTA Bilateral Agreements,
  CN=Bells, OU=Computer Science,
  O=University College London, C=GB





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  To represent information on the MTA which has the Distinguished Name:

  CN=Q3T21, ADMD=Gold 400, C=GB

  There would be an entry in this table with the Relative Distinguished
  Name of the table entry being the Distinguished Name of the MTA being
  referred to.  The MTA Bilateral information would be an attribute in
  this entry.  Using a non-standard notation, the Distinguished Name of
  the table entry is:

  DistinguishedNameTableKey=<CN=Q3T21, ADMD=Gold 400, C=GB>,
  CN=MTA Bilateral Agreements,
  CN=Bells, OU=Computer Science,
  O=University College London, C=GB

2  Representing Subtrees

  A subtree is similar to a table, except that the keys are constructed
  as a distinguished name hierarchy relative to the location of the
  subtree in the DIT. The subtree effectively starts a private "root",
  and has distinguished names relative to this root.  Typically, this
  approach is used to associate local information with global objects.
  The schema used is defined in Figure 2.  Functionally, this is
  equivalent to a table with distinguished name keys.  The table
  approach is best when the tree is very sparse.  This approach is
  better for subtrees which are more populated.

  The subtree object class defines the root for a subtree in an
  analogous means to the table.  Information within the subtree will
  generally be defined in the same way as for the global object, and so

  subtree OBJECT-CLASS ::= {
      SUBCLASS OF {top}
      MUST CONTAIN {commonName}
      MAY CONTAIN {manager}
      ID oc-subtree}

                    Figure 2:  Representing Subtrees


  no specific object classes for subtree entries are needed.

  For example consider University College London.

  O=University College London, C=GB






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  Suppose that the UCL needs a private subtree, with interesting
  information about directory objects.  The table might be named as:

  CN=private subtree,
  O=University College London, C=GB

  UCL specific information on Inria might be stored in the entry:

  O=Inria, C=FR,
  CN=private subtree,
  O=University College London, C=GB

  Practical examples of this mapping are given in [2].

3  Acknowledgments

  Acknowledgments for work on this document are given in [2].

References

  [1] The Directory --- overview of concepts, models and services,
      1993. CCITT X.500 Series Recommendations.

  [2] Kille, S.E., "X.400-MHS use of the X.500 directory to support
      X.400-MHS routing," RFC 1801, June 1995.

4  Security Considerations

  Security considerations are not discussed in this memo.

5  Author's Address

  Steve Kille
  Isode Ltd
  The Dome
  The Square
  Richmond
  TW9 1DT
  England

  Phone:  +44-181-332-9091
  EMail:  [email protected]









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RFC 2293            Table and Subtrees in the X.500           March 1998


A  Object Identifier Assignment


mhs-ds OBJECT IDENTIFIER ::= {iso(1) org(3) dod(6) internet(1)
         private(4) enterprises(1) isode-consortium (453) mhs-ds (7)}

tables OBJECT IDENTIFIER ::= {mhs-ds 1}

oc OBJECT IDENTIFIER ::= {tables 1}
at OBJECT IDENTIFIER ::= {tables 2}

oc-subtree OBJECT IDENTIFIER ::= {oc 1}
oc-table OBJECT IDENTIFIER ::= {oc 2}                               10
oc-table-entry OBJECT IDENTIFIER ::= {oc 3}
oc-text-table-entry OBJECT IDENTIFIER ::= {oc 4}
oc-distinguished-name-table-entry  OBJECT IDENTIFIER ::= {oc 5}

at-text-table-key OBJECT IDENTIFIER ::= {at 1}
at-text-table-value OBJECT IDENTIFIER ::= {at 2}
at-distinguished-name-table-key OBJECT IDENTIFIER ::= {at 3}

               Figure 3:  Object Identifier Assignment





























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Full Copyright Statement

  Copyright (C) The Internet Society (1998).  All Rights Reserved.

  This document and translations of it may be copied and furnished to
  others, and derivative works that comment on or otherwise explain it
  or assist in its implementation may be prepared, copied, published
  and distributed, in whole or in part, without restriction of any
  kind, provided that the above copyright notice and this paragraph are
  included on all such copies and derivative works.  However, this
  document itself may not be modified in any way, such as by removing
  the copyright notice or references to the Internet Society or other
  Internet organizations, except as needed for the purpose of
  developing Internet standards in which case the procedures for
  copyrights defined in the Internet Standards process must be
  followed, or as required to translate it into languages other than
  English.

  The limited permissions granted above are perpetual and will not be
  revoked by the Internet Society or its successors or assigns.

  This document and the information contained herein is provided on an
  "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
  TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
  BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
  HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
  MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
























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