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452 lines
12 KiB
Plaintext
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Network Working Group S. Kille
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Request for Comments: 2293 Isode Ltd.
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Obsoletes: 1837 March 1998
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Category: Standards Track
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Representing Tables and Subtrees in the X.500 Directory
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Status of this Memo
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This document specifies an Internet standards track protocol for the
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Internet community, and requests discussion and suggestions for
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improvements. Please refer to the current edition of the "Internet
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Official Protocol Standards" (STD 1) for the standardization state
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and status of this protocol. Distribution of this memo is unlimited.
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Copyright Notice
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Copyright (C) The Internet Society (1998). All Rights Reserved.
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Abstract
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This document defines techniques for representing two types of
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information mapping in the OSI Directory [1].
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1. Mapping from a key to a value (or set of values), as might
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be done in a table lookup.
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2. Mapping from a distinguished name to an associated
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value (or values), where the values are not defined by the owner
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of the entry. This is achieved by use of a directory subtree.
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These techniques were developed for supporting MHS use of Directory
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[2], but are specified separately as they have more general
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applicability.
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Kille Standards Track [Page 1]
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RFC 2293 Table and Subtrees in the X.500 March 1998
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1 Representing Flat Tables
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Before considering specific function, a general purpose technique for
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representing tables in the directory is introduced. The schema for
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this is given in Figure 1. A table can be considered as an unordered
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set of key to (single or multiple) value mappings, where the key
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cannot be represented as a global name. There are four reasons why
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this may occur:
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1. The object does not have a natural global name.
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2. The object can only be named effectively in the context of
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being a key to a binding. In this case, the object will be given
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a natural global name by the table.
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3. The object has a global name, and the table is being used
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to associate parameters with this object, in cases where they
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cannot be placed in the objects global entry. Reasons why they
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might not be so placed include:
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o The object does not have a directory entry
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o There is no authority to place the parameters in the
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global entry
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o The parameters are not global --- they only make sense
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in the context of the table.
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4. It is desirable to group information together as a
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performance optimization, so that the block of information may be
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widely replicated.
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A table is represented as a single level subtree. The root of the
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subtree is an entry of object class Table. This is named with a
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common name descriptive of the table. The table will be located
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somewhere appropriate to its function. If a table is private to an
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MTA, it will be below the MTA's entry. If it is shared by MTA's in
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an organization, it will be located under the organization.
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The generic table entry contains only a description. All instances
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will be subclassed, and the subclass will define the naming
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attribute. Two subclasses are defined:
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Kille Standards Track [Page 2]
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RFC 2293 Table and Subtrees in the X.500 March 1998
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table OBJECT-CLASS ::= {
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SUBCLASS OF {top}
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MUST CONTAIN {commonName}
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MAY CONTAIN {manager}
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ID oc-table}
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tableEntry OBJECT-CLASS ::= {
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SUBCLASS OF {top}
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MAY CONTAIN {description} 10
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ID oc-table-entry}
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textTableEntry OBJECT-CLASS ::= {
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SUBCLASS OF {tableEntry}
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MUST CONTAIN {textTableKey}
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MAY CONTAIN {textTableValue}
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ID oc-text-table-entry}
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textTableKey ATTRIBUTE ::= {
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SUBTYPE OF name 20
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WITH SYNTAX DirectoryString {ub-name}
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ID at-text-table-key}
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textTableValue ATTRIBUTE ::= {
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SUBTYPE OF name
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WITH SYNTAX DirectoryString {ub-description}
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ID at-text-table-value}
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distinguishedNameTableEntry OBJECT-CLASS ::= {
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SUBCLASS OF {tableEntry} 30
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MUST CONTAIN {distinguishedNameTableKey}
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ID oc-distinguished-name-table-entry}
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distinguishedNameTableKey ATTRIBUTE ::= {
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SUBTYPE OF distinguishedName
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ID at-distinguished-name-table-key}
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Figure 1: Representing Tables
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1. TextEntry, which define table entries with text keys,
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which may have single or multiple values of any type. An
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attribute is defined to allow a text value, to support the
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frequent text key to text value mapping. Additional values may
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be defined.
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Kille Standards Track [Page 3]
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RFC 2293 Table and Subtrees in the X.500 March 1998
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2. DistinguishedNameEntry. This is used for associating
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information with globally defined objects. This approach should
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be used where the number of objects in the table is small or very
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sparsely spread over the DIT. In other cases where there are many
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objects or the objects are tightly clustered in the DIT, the
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subtree approach defined in Section 2 will be preferable. No
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value attributes are defined for this type of entry. An
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application of this will make appropriate subtyping to define the
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needed values.
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This is best illustrated by example. Consider the MTA:
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CN=Bells, OU=Computer Science,
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O=University College London, C=GB
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Suppose that the MTA needs a table mapping from private keys to fully
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qualified domain names (this example is fictitious). The table might
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be named as:
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CN=domain-nicknames,
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CN=Bells, OU=Computer Science,
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O=University College London, C=GB
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To represent a mapping in this table from "euclid" to
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"bloomsbury.ac.uk", the entry:
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TextTableKey=euclid, CN=domain-nicknames,
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CN=Bells, OU=Computer Science,
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O=University College London, C=GB
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will contain the attribute:
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TextTableValue=bloomsbury.ac.uk
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A second example, showing the use of DistinguishedNameEntry is now
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given. Consider again the MTA:
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CN=Bells, OU=Computer Science,
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O=University College London, C=GB
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Suppose that the MTA needs a table mapping from MTA Name to bilateral
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agreement information of that MTA. The table might be named as:
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CN=MTA Bilateral Agreements,
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CN=Bells, OU=Computer Science,
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O=University College London, C=GB
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Kille Standards Track [Page 4]
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RFC 2293 Table and Subtrees in the X.500 March 1998
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To represent information on the MTA which has the Distinguished Name:
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CN=Q3T21, ADMD=Gold 400, C=GB
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There would be an entry in this table with the Relative Distinguished
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Name of the table entry being the Distinguished Name of the MTA being
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referred to. The MTA Bilateral information would be an attribute in
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this entry. Using a non-standard notation, the Distinguished Name of
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the table entry is:
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DistinguishedNameTableKey=<CN=Q3T21, ADMD=Gold 400, C=GB>,
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CN=MTA Bilateral Agreements,
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CN=Bells, OU=Computer Science,
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O=University College London, C=GB
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2 Representing Subtrees
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A subtree is similar to a table, except that the keys are constructed
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as a distinguished name hierarchy relative to the location of the
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subtree in the DIT. The subtree effectively starts a private "root",
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and has distinguished names relative to this root. Typically, this
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approach is used to associate local information with global objects.
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The schema used is defined in Figure 2. Functionally, this is
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equivalent to a table with distinguished name keys. The table
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approach is best when the tree is very sparse. This approach is
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better for subtrees which are more populated.
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The subtree object class defines the root for a subtree in an
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analogous means to the table. Information within the subtree will
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generally be defined in the same way as for the global object, and so
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subtree OBJECT-CLASS ::= {
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SUBCLASS OF {top}
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MUST CONTAIN {commonName}
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MAY CONTAIN {manager}
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ID oc-subtree}
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Figure 2: Representing Subtrees
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no specific object classes for subtree entries are needed.
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For example consider University College London.
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O=University College London, C=GB
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Kille Standards Track [Page 5]
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RFC 2293 Table and Subtrees in the X.500 March 1998
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Suppose that the UCL needs a private subtree, with interesting
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information about directory objects. The table might be named as:
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CN=private subtree,
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O=University College London, C=GB
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UCL specific information on Inria might be stored in the entry:
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O=Inria, C=FR,
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CN=private subtree,
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O=University College London, C=GB
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Practical examples of this mapping are given in [2].
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3 Acknowledgments
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Acknowledgments for work on this document are given in [2].
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References
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[1] The Directory --- overview of concepts, models and services,
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1993. CCITT X.500 Series Recommendations.
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[2] Kille, S.E., "X.400-MHS use of the X.500 directory to support
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X.400-MHS routing," RFC 1801, June 1995.
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4 Security Considerations
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Security considerations are not discussed in this memo.
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5 Author's Address
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Steve Kille
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Isode Ltd
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The Dome
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The Square
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Richmond
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TW9 1DT
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England
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Phone: +44-181-332-9091
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EMail: S.Kille@ISODE.COM
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Kille Standards Track [Page 6]
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RFC 2293 Table and Subtrees in the X.500 March 1998
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A Object Identifier Assignment
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mhs-ds OBJECT IDENTIFIER ::= {iso(1) org(3) dod(6) internet(1)
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private(4) enterprises(1) isode-consortium (453) mhs-ds (7)}
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tables OBJECT IDENTIFIER ::= {mhs-ds 1}
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oc OBJECT IDENTIFIER ::= {tables 1}
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at OBJECT IDENTIFIER ::= {tables 2}
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oc-subtree OBJECT IDENTIFIER ::= {oc 1}
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oc-table OBJECT IDENTIFIER ::= {oc 2} 10
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oc-table-entry OBJECT IDENTIFIER ::= {oc 3}
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oc-text-table-entry OBJECT IDENTIFIER ::= {oc 4}
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oc-distinguished-name-table-entry OBJECT IDENTIFIER ::= {oc 5}
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at-text-table-key OBJECT IDENTIFIER ::= {at 1}
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at-text-table-value OBJECT IDENTIFIER ::= {at 2}
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at-distinguished-name-table-key OBJECT IDENTIFIER ::= {at 3}
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Figure 3: Object Identifier Assignment
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Kille Standards Track [Page 7]
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RFC 2293 Table and Subtrees in the X.500 March 1998
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Full Copyright Statement
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Copyright (C) The Internet Society (1998). All Rights Reserved.
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This document and translations of it may be copied and furnished to
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others, and derivative works that comment on or otherwise explain it
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or assist in its implementation may be prepared, copied, published
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and distributed, in whole or in part, without restriction of any
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kind, provided that the above copyright notice and this paragraph are
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included on all such copies and derivative works. However, this
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document itself may not be modified in any way, such as by removing
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the copyright notice or references to the Internet Society or other
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Internet organizations, except as needed for the purpose of
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developing Internet standards in which case the procedures for
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copyrights defined in the Internet Standards process must be
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followed, or as required to translate it into languages other than
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English.
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The limited permissions granted above are perpetual and will not be
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revoked by the Internet Society or its successors or assigns.
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This document and the information contained herein is provided on an
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"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
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TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
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HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
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MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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Kille Standards Track [Page 8]
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