Network Working Group
Request for Comments: 2927
Category: Informational

M. Wahl
Sun Microsystems, Inc.
September 2000

MIME Directory Profile for LDAP Schema

Status of this Memo

This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.

Copyright Notice

Abstract

This document defines a multipurpose internet mail extensions (MIME) directory profile for holding a lightweight directory access protocol (LDAP) schema. It is intended for communication with the Internet schema listing service.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [4].

1. Overview

This document defines how a MIME type may be used to transfer a single LDAPv3 schema definition.

A schema for use with LDAPv3 consists of any number of object class, attribute type, matching rule and syntax definitions. These concepts are defined in the LDAPv3 protocol definition [2]. The schema MAY have a numeric OID assigned to it by a schema listing or registration service.

A schema may import definitions from another schema. Schema imports are not, however, transitive.

For example, a schema contains a definition for a "modem" object class, which is to be defined as a subclass of the X.521 "device" object class. In this case, the schema MUST import the definitions of X.521.

2. The "schema-ldap-0" MIME Directory Profile Registration

This profile is identified by the following registration template information.

   To: ietf-mime-direct@imc.org
   Subject: Registration of text/directory MIME profile "schema-ldap-0"
   
   Profile name: schema-ldap-0

Profile purpose: To represent a schema defined for use with LDAPv3 servers.

   Profile types: SOURCE, ldapSchemas, attributeTypes, matchingRules,
   objectClasses, matchingRuleUse, ldapSyntaxes

Profile special notes:

The charset parameter MUST be present on the MIME content, and the value of this parameter MUST be "utf-8". This ensures that schema values can be used in LDAPv3 attribute values without a character set translation.

Neither the "BEGIN" and "END" types nor type grouping are used in contents of this profile.

All of the types in this profile with the exception of ldapSchemas may be multi-valued. Each value is present on its own contentline. Values may be present in any order, and need not be arranged by type.

The "SOURCE" type is optional, and if values are present they SHOULD be URIs of the "ldap" form. If the URI is of the "ldap" form, the object indicated by the URI is a subschema entry. The use of other forms are reserved for future applications.

In this version of the profile, exactly one value of the ldapSchemas type MUST be present. (Later versions of the profile may permit multiple ldapSchemas values to be present in a content.)

Implementors should note that there will likely be values of the profile types in most contents much longer than 76 bytes. In addition, there may be non-ASCII characters and embedded CRLFs inside of values, which could require either quoting of the value or use of a content transfer encoding.

If a contentline in a particular content contains a "context" parameter and the value of that parameter is not "ldap", then that contentline SHOULD be ignored.

   Intended usage: COMMON

3. MIME Directory Type Registrations

This document defines all the types, with the exception of "SOURCE" used in the schema-ldap-0 profile. The "SOURCE" type is defined in [1]. These types are primarily intended for use in the "schema- ldap-0" directory profile, although they may be applicable to other profiles defined in the future.

3.1. ldapSchemas

   To: ietf-mime-direct@imc.org
   Subject: Registration of text/directory MIME type ldapSchemas
   
   Type name: ldapSchemas

Type purpose: To represent the LDAPv3 attribute "ldapSchemas", defined in section A.1.

   Type encoding: 8bit

Type valuetype: text, encoded according to the BNF of section A.2.

Type special notes: Each value of this type specifies the contents of an LDAP schema definition. A definition of each object class, attribute, matching rule, matching rule use and syntax referenced in a value of ldapSchemas MUST either be defined in one of the schemas referenced in the "IMPORTS" field, or present in the content containing this value.

   Intended usage: COMMON

3.2. attributeTypes

   To: ietf-mime-direct@imc.org
   Subject: Registration of text/directory MIME type attributeTypes
   
   Type name: attributeTypes

Type purpose: To represent the LDAPv3 attribute "attributeTypes", defined in section 5.1.6 of [4].

   Type encoding: 8bit

Type valuetype: text, encoded according to the BNF of "AttributeTypeDescription" given in section 4.2 of [4].

Type special notes: Each value of the type specifies one LDAPv3 attribute type definition. The syntax and matching rules referenced in a value of attributeTypes MUST either be present in this content, or defined in one of the schemas referenced in the "IMPORTS" field of the ldapSchemas line.

   Intended usage: COMMON

3.3. matchingRules

   To: ietf-mime-direct@imc.org
   Subject: Registration of text/directory MIME type matchingRules
   
   Type name: matchingRules

Type purpose: To represent the LDAPv3 attribute "matchingRules", defined in section 5.1.8 of [4].

   Type encoding: 8bit

Type valuetype: text, encoded according to the BNF of "MatchingRuleDescription" given in section 4.5 of [4].

Type special notes: Each value of the type specifies one matching rule definition. The syntax reference in a value of matchingRules MUST either be present in this content, or defined in one of the schemas referenced in the "IMPORTS" field of the ldapSchemas line.

   Intended usage: COMMON

3.4. objectClasses

   To: ietf-mime-direct@imc.org
   Subject: Registration of text/directory MIME type objectClasses
   
   Type name: objectClasses

Type purpose: To represent the LDAPv3 attribute "objectClasses", defined in section 5.1.7 of [4].

   Type encoding: 8bit

Type valuetype: text, encoded according to the BNF of "ObjectClassDescription" given in section 4.4 of [4].

Type special notes: Each value of the type specifies one LDAPv3 object class definition. The attributes and object classes referenced in a value of objectClasses MUST either be present in this content, or defined in one of the schema referenced in the "IMPORTS" field of the ldapSchemas line.

   Intended usage: COMMON

3.5. matchingRuleUse

   To: ietf-mime-direct@imc.org
   Subject: Registration of text/directory MIME type matchingRuleUse
   
   Type name: matchingRuleUse

Type purpose: To represent the LDAPv3 attribute "matchingRuleUse", defined in section 5.1.9 of [4].

   Type encoding: 8bit

Type valuetype: text, encoded according to the BNF of "MatchingRuleUseDescription" given in section 4.5 of [4].

Type special notes: Each value of the type specifies a relationship between a matching rule and attribute types. The matching rule and attribute types referenced in a value of matchingRuleUse MUST either be present in this content, or defined in one of the schemas referenced in the "IMPORTS" statement of the ldapSchemas line.

   Intended usage: COMMON

3.6. ldapSyntaxes

   To: ietf-mime-direct@imc.org
   Subject: Registration of text/directory MIME type ldapSyntaxes
   
   Type name: ldapSyntaxes

Type purpose: To represent the LDAPv3 attribute "ldapSyntaxes", defined in section 5.3.1 of [3].

   Type encoding: 8bit

Type valuetype: text, encoded according to the BNF of "SyntaxDescription" given in section 4.3.3 of [3].

Type special notes: Each value of this type specifies a single LDAPv3 attribute value syntax.

   Intended usage: COMMON

3. Example

   From: Whomever@wherever.com
   To: Someone@somewhere.com
   Subject: schema information
   MIME-Version: 1.0
   Message-Id: <ids1@wherever.com>
   Content-Type: text/directory; profile="schema-ldap-0";charset="utf-8"
   Content-Transfer-Encoding: Quoted-Printable
   ldapSchemas: ( 1.2.3.4 NAME 'bogus schema' CLASSES ( top $ thing ) =
   ATTRIBUTES ( objectClass $ name ) SYNTAXES ( =
   1.3.6.1.4.1.1466.115.121.1.38 $ 1.3.6.1.4.1.1466.115.121.1.15 ) )
   attributeTypes: ( 2.5.4.0 NAME 'objectClass' SYNTAX =
   1.3.6.1.4.1.1466.115.121.1.38 )
   objectClasses: ( 2.5.6.0 NAME 'top' ABSTRACT MUST objectClass )
   attributeTypes: ( 2.5.4.41 NAME 'name' SYNTAX =
   1.3.6.1.4.1.1466.115.121.1.15{32768} )
   objectClasses: ( 2.5.6.999 NAME 'thing' MUST name )
   ldapSyntaxes: ( 1.3.6.1.4.1.1466.115.121.1.15 DESC 'String' )
   ldapSyntaxes: ( 1.3.6.1.4.1.1466.115.121.1.38 DESC 'OID' )

4. Security Considerations

A MIME body part containing an text/directory of the schema-ldap-0 profile may be incorporated in a digitally signed MIME content, which can be used to verify that the body part has not been modified in transit. When the signer has been certified by a trusted third party service, it may also be possible to verify the origin of the content.

5. Bibliography

   [1] Howes, T., Smith, M. and F. Dawson, "A MIME Content-Type for
       Directory Information", RFC 2425, September 1998.
   
   [2] Wahl, M., Howes, T. and S. Kille, "Lightweight Directory Access
       Protocol (v3)", RFC 2251, December 1997.
   
   [3] Wahl, M., Coulbeck, A., Howes, T. and S. Kille, "Lightweight
       Directory Access Protocol (v3): Attribute Syntax Definitions",
       RFC 2252, December 1997.
   
   [4] Bradner, S., "Key words for use in RFCs to Indicate Requirement
       Levels", BCP 14, RFC 2119, March 1997.

6. Author's Address

Mark Wahl
Sun Microsystems, Inc.
8911 Capital of Texas Hwy Suite 4140
Austin, TX 78759
USA

   EMail:  Mark.Wahl@sun.com

Appendix A

This appendix defines two new attributes which could be present in an subschema entry. These attributes could be added to a future revision of the LDAP attribute definition [3].

A.1. ldapSchemas attribute type definition

      ( 1.3.6.1.4.1.1466.101.120.17 NAME 'ldapSchemas'
        SYNTAX 1.3.6.1.4.1.1466.115.121.1.56 USAGE directoryOperation )

Each value of the ldapSchemas attribute defines one schema. Its syntax, given in section A.2, contains the elements needed for an LDAPv3 server to correctly process operations which use the definitions from this syntax.

A.2. LDAP Schema Definition syntax definition

      ( 1.3.6.1.4.1.1466.115.121.1.56 DESC 'LDAP Schema Definition' )

Values in this syntax are represented according to the following BNF:

LdapSchema = "(" whsp

numericoid whsp
[ "NAME" qdescrs ]
[ "OBSOLETE" whsp ]
[ "IMPORTS" oids ]
[ "CLASSES" oids ]
[ "ATTRIBUTES" oids ]
[ "MATCHING-RULES" oids ]
[ "SYNTAXES" oids ]
whsp ")"

The numericoid field uniquely identifies the schema. A new OID should be assigned if any of the fields of the schema change. It is not possible to import definitions from a schema until an OID has been assigned to it.

The "NAME" field contains optional human-readable labels for the schema.

The "OBSOLETE" field is present if the schema is obsolete.

The "IMPORTS" field lists the OIDs of other schemas which are to be incorporated by reference into this schema. It is an error to have an attribute type or object class defined in a schema with the same name but a different OID as an attribute type or object class in an imported schema. It is also an error to import from two schema definitions in which there are attribute types or object classes with the same names but different OIDs.

The "CLASSES" field lists the OIDs of object classes defined in this schema. A schema need not contain any object class definitions. A schema must not contain two object class definitions of the same name but with different OIDs.

The "ATTRIBUTES" field lists the OIDs of attribute types defined in this schema. A schema need not contain any object class definitions. A schema must not contain two attribute type definitions of the same name but with different OIDs.

The "MATCHING-RULES" field lists the OIDs of matching rules defined in this schema. A schema need not contain any matching rules.

The "SYNTAXES" field lists the OIDs of syntaxes defined in this schema. A schema need not contain any syntaxes.

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Acknowledgement

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