Internet-Draft                                       D.W.Chadwick
LDAPExt WG                                         University of Salford
Intended Category: Standards Track
Expires: 20 February 2000                            20 August 1999

                        Returning Matched Values with LDAPv3
                       <draft-ietf-ldapext-matchedval-00.txt>

STATUS OF THIS MEMO

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

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This Internet-Draft expires on 20 February 2000. Comments and
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ABSTRACT

This document describes a control for the Lightweight Directory
Access Protocol v3 that is used to return a subset of attribute
values from an entry, specifically, only those values that
contributed to the search filter evaluating to TRUE.

. Introduction

When reading an attribute from an entry using LDAP v2 [1] or LDAPv3
[2], it is normally only possible to read either the attribute type,
or the attribute type and all its values. It is not possible to
selectively read just a few of the attribute values. If an attribute
holds many values, for example, the userCertificate attribute, or the
subschema publishing operational attributes objectClasses and
attributeTypes [3], then it may be desirable for the user to be able
to selectively retrieve a subset of the values, specifically, those
attributes that match the selection criteria as specified by the user
in the filter. This Internet Draft specifies an LDAPv3 control to
enable a user to do just that i.e. return only those values that
matched (i.e. returned TRUE to) one or more filter items.

The control has been described in such as way as to be compatible
with the matchedValuesOnly boolean of the X.500 DAP [4] Search
argument.

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 [5].

. The matchedValuesOnly Control

The matchedValuesOnly control MAY be critical or non-critical as
determined by the user. It is only applicable to the Search
operation, and SHALL be ignored by the server if it is present on any
other LDAP operation (even if marked critical on such operations).

The object identifier for this control is 1.2.826.0.1.3344810.2.2

The value for this control is a BOOLEAN. An absent value implies
FALSE.

The effects of this control on the Search operation are as follows.

i) Every attribute value that evaluates TRUE against one or more
filter items, excluding the ignored filter items (see below),
is logically marked by the server as contributing to the filter
matching.
ii) If the user requests that the contributing attribute types and
their values are returned in the Search result (by placing the
attribute type in the AttributeDescriptionList, and by setting
the typesOnly BOOLEAN to FALSE), then only the attribute values
marked as contributing are returned, whilst the other values of
the same attribute (if there are any) are not returned.
iii) Attributes that are to be returned to the user, and that have
no values marked as contributing, have all their values
returned to the user.
iv) Attributes that have values marked as contributing, but which
are not asked to be returned to the user, are not returned and
the marking is of no practical value.

Certain filters are ignored for the purposes of marking the attribute
values as contributing. These are:

the present filter, since this filter does not test against any
attribute values;
the equalityMatch filter, since if the user is able to specify
the complete attribute value exactly, then there is very little
to be gained from having only this value returned;
any negated filter, since this would have the effect of marking
all the attribute values except the one(s) that matched the
non-negated filter.

Note 1. The inclusion of equalityMatch in the list above maintains
compatibility with the X.500 standard.
Note 2. If the equality matching rule does not require the entire
attribute value to be presented by the user, then there is something
to be gained from asking for this value only to be returned in its
entirety. This can be achieved by using the extensibleMatch filter
and using the equality matching rule as the matching rule.

. Security Considerations

This Internet Draft does not discuss security issues at all.
Attribute values SHALL only be returned if the access controls
applied by the LDAP server allow them to be returned, and in this
respect the effect of the matchedValuesOnly control is of no
consequence.

 Copyright

Copyright (C) The Internet Society (date). 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.

. References

[] Yeong, W., Howes, T., and Kille, S. "Lightweight Directory Access
Protocol", RFC 1777, March 1995.
[2] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access
Protocol (v3)", Dec. 1997, RFC 2251
[3] M. Wahl, A. Coulbeck, T. Howes, S. Kille, "Lightweight Directory
Access Protocol (v3): Attribute Syntax Definitions", RFC 2252, Dec
1997
[4] ITU-T Rec. X.511, "The Directory: Abstract  Service  Definition",
1993.
[5] S.Bradner. "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997.

 Authors Address

David Chadwick
IS Institute
University of Salford
Salford
England
M5 4WT

Email: d.w.chadwick@salford.ac.uk

Internet-Draft   Returning Matched Values with LDAPv3  20 August 1999

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