





INTERNET-DRAFT                                      Kurt D. Zeilenga
Intended Category: Standard Track                OpenLDAP Foundation
Expires in six months                                25 October 2003



                   LDAP Absolute True and False Filters
                     <draft-zeilenga-ldap-t-f-07.txt>


Status of this Memo

  This document is an Internet-Draft and is in full conformance with all
  provisions of Section 10 of RFC2026.

  This document is intended to be, after appropriate review and
  revision, submitted to the RFC Editor as a Standard Track document.
  Distribution of this memo is unlimited.  Technical discussion of this
  document will take place on the IETF LDAP Extensions mailing list
  <ldapext@ietf.org>.  Please send editorial comments directly to the
  author <Kurt@OpenLDAP.org>.

  Internet-Drafts are working documents of the Internet Engineering Task
  Force (IETF), its areas, and its working groups.  Note that other
  groups may also distribute working documents as Internet-Drafts.
  Internet-Drafts are draft documents valid for a maximum of six months
  and may be updated, replaced, or obsoleted by other documents at any
  time.  It is inappropriate to use Internet-Drafts as reference
  material or to cite them other than as ``work in progress.''

  The list of current Internet-Drafts can be accessed at
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  Copyright (C) The Internet Society (2003).  All Rights Reserved.

  Please see the Full Copyright section near the end of this document
  for more information.


Abstract

  This document extends the Lightweight Directory Access Protocol (LDAP)
  to support absolute True and False filters based upon similar
  capabilities found in X.500 directory systems.  The document also
  extends the String Representation of LDAP Search Filters to support
  these filters.



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1.  Background

  The X.500 Directory Access Protocol (DAP) [X.511] supports absolute
  True and False assertions.  An 'and' filter with zero elements always
  evaluates to True.  An 'or' filter with zero elements always evaluates
  to False.  These filters are commonly used when requesting DSA-
  specific Entries (DSEs) which do not necessarily have 'objectClass'
  attributes.  That is, where "(objectClass=*)" may evaluate to False.

  While LDAPv2 [RFC1777][RFC3494] placed no restriction on the number of
  elements in 'and' and 'or' filter sets, the LDAPv2 string
  representation [RFC1960] could not represent empty 'and' and 'or'
  filter sets.  Due to this, absolute True or False filters were
  (unfortunately) eliminated from LDAPv3 [RFC3377].

  This documents extends LDAPv3 to support absolute True and False
  matches by allowing empty 'and' and 'or' in Search filters [RFC2251]
  and extends the filter string representation [RFC2254] to allow empty
  filter lists.

  This feature is intended to allow a more direct mapping between DAP
  and LDAP (as needed to implement DAP-to-LDAP gateways).


  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 BCP 14 [RFC2119].


2.  Absolute True and False Filters

  Implementations of this extension SHALL allow 'and' and 'or' choices
  with zero filter elements.

  An 'and' filter consisting of an empty set of filters SHALL evaluate
  to True.  This filter is represented by the string "(&)".

  An 'or' filter consisting of an empty set of filters SHALL evaluate to
  False.  This filter is represented by the string "(|)".

  Servers supporting this feature SHOULD publish the Object Identifier
  (OID) 1.3.6.1.4.1.4203.1.5.3 as a value of the 'supportedFeatures'
  [FEATURES] attribute in the root DSE.

  Clients supporting this feature SHOULD NOT use the feature unless they
  have knowledge the server supports it.





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3.  Security Considerations

  The (re)introduction of absolute True and False filters is not
  believed to raise any new security considerations.

  Implementors of this (or any) LDAPv3 extension should be familiar with
  general LDAPv3 security considerations [RFC3377].


4.  IANA Considerations

  The OID 1.3.6.1.4.1.4203.1.5.3 identifies the feature described above.
  This OID was assigned [ASSIGN] by OpenLDAP Foundation, under its
  IANA-assigned private enterprise allocation [PRIVATE], for use in this
  specification.

  Registration of this feature is requested [FEATURES][RFC3383].

  Subject: Request for LDAP Protocol Mechanism Registration
  Object Identifier: 1.3.6.1.4.1.4203.1.5.3
  Description: T/F Filters
  Person & email address to contact for further information:
       Kurt Zeilenga <kurt@openldap.org>
  Usage: Feature
  Specification: RFC XXXX
  Author/Change Controller: IESG
  Comments: none


5.  Author's Address

  Kurt D. Zeilenga
  OpenLDAP Foundation
  <Kurt@OpenLDAP.org>


6. Normative References

  [RFC2119]     Bradner, S., "Key words for use in RFCs to Indicate
                Requirement Levels", BCP 14 (also RFC 2119), March 1997.

  [RFC2251]     Wahl, M., T. Howes and S. Kille, "Lightweight Directory
                Access Protocol (v3)", RFC 2251, December 1997.

  [RFC2254]     Howes, T., "A String Representation of LDAP Search
                Filters", RFC 2254, December 1997.

  [RFC3377]     Hodges, J. and R. Morgan, "Lightweight Directory Access



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                Protocol (v3): Technical Specification", RFC 3377,
                September 2002.

  [FEATURES]    Zeilenga, K., "Feature Discovery in LDAP",
                draft-zeilenga-ldap-features-xx.txt, a work in progress.


7. Informative References

  [RFC1777]     Yeong, W., Howes, T., and S. Kille, "Lightweight
                Directory Access Protocol", RFC 1777, March 1995.

  [RFC1960]     Howes, T., "A String Representation of LDAP Search
                Filters", RFC 1960, June 1996.

  [RFC3383]     Zeilenga, K., "IANA Considerations for LDAP", BCP 64
                (also RFC 3383), September 2002.

  [RFC3494]     Zeilenga, K., "Lightweight Directory Access Protocol
                version 2 (LDAPv2) to Historic Status", RFC 3494, March
                2003.

  [X.500]       International Telecommunication Union -
                Telecommunication Standardization Sector, "The Directory
                -- Overview of concepts, models and services,"
                X.500(1993) (also ISO/IEC 9594-1:1994).

  [X.501]       International Telecommunication Union -
                Telecommunication Standardization Sector, "The Directory
                -- Models," X.501(1993) (also ISO/IEC 9594-2:1994).

  [ASSIGN]      OpenLDAP Foundation, "OpenLDAP OID Delegations",
                http://www.openldap.org/foundation/oid-delegate.txt.

  [PRIVATE]     IANA, "Private Enterprise Numbers",
                http://www.iana.org/assignments/enterprise-numbers.



Intellectual Property Rights

  The IETF takes no position regarding the validity or scope of any
  intellectual property or other rights that might be claimed to pertain
  to the implementation or use of the technology described in this
  document or the extent to which any license under such rights might or
  might not be available; neither does it represent that it has made any
  effort to identify any such rights.  Information on the IETF's
  procedures with respect to rights in standards-track and



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  standards-related documentation can be found in BCP-11.  Copies of
  claims of rights made available for publication and any assurances of
  licenses to be made available, or the result of an attempt made to
  obtain a general license or permission for the use of such proprietary
  rights by implementors or users of this specification can be obtained
  from the IETF Secretariat.

  The IETF invites any interested party to bring to its attention any
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  this standard.  Please address the information to the IETF Executive
  Director.



Full Copyright

  Copyright (C) The Internet Society (2003). 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 implmentation 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.




















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