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Network Working Group                                            S. KilleRequest for Comments: 2293                                     Isode Ltd.Obsoletes:1837                                                March 1998Category: Standards TrackRepresenting Tables and Subtrees in the X.500 DirectoryStatus 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.Kille                       Standards Track                     [Page 1]

RFC 2293            Table and Subtrees in the X.500           March 19981  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:Kille                       Standards Track                     [Page 2]

RFC 2293            Table and Subtrees in the X.500           March 1998table 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.Kille                       Standards Track                     [Page 3]

RFC 2293            Table and Subtrees in the X.500           March 1998   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 inSection 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=GBKille                       Standards Track                     [Page 4]

RFC 2293            Table and Subtrees in the X.500           March 1998   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=GB2  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=GBKille                       Standards Track                     [Page 5]

RFC 2293            Table and Subtrees in the X.500           March 1998   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:  S.Kille@ISODE.COMKille                       Standards Track                     [Page 6]

RFC 2293            Table and Subtrees in the X.500           March 1998A  Object Identifier Assignmentmhs-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}                               10oc-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 AssignmentKille                       Standards Track                     [Page 7]

RFC 2293            Table and Subtrees in the X.500           March 1998Full 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.Kille                       Standards Track                     [Page 8]