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LDAPEXT Working Group J. Sermersheim
Internet Draft Novell, Inc
Document: draft-ietf-ldapext-ldapv3-dupent-03.txt March 2000
Category: Proposed Standard
LDAP Control for a Duplicate Entry Representation of Search Results
1. Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026 [1].
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
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
2. Abstract
This document describes a Duplicate Entry Representation control
extension for the LDAP Search operation. By using the control with
an LDAP search, a client requests that the server return separate
entries for each value held in the specified attributes. For
instance, if a specified attribute of an entry holds multiple
values, the search operation will return multiple instances of that
entry, each instance holding a separate single value in that
attribute.
3. Overview
The Server-Side Sorting control [SSS] allows the server to order
search result entries based on attribute values (sort keys). It
does not allow one to specify behavior when an attribute contains
multiple values. The default behavior, as outlined in 7.9 of
[X.511], is to use the smallest value as the sort key.
An application may need to produce an ordered list of entries,
sorted by a multi-valued attribute, where each attribute value is
represented in the list. In order to do this, a separate control is
needed which causes the set of entries to be expanded sufficiently
to represent each attribute value prior to sorting.
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LDAP Control for a Duplicate Entry Representation of Search Results
This document describes controls, which allow duplicate entries in
the result set of search, where each entry represents a distinct
value of a given multiple valued attribute.
An example of this would be a sorted list of all telephone numbers
in an organization. Because any entry may have multiple telephone
numbers, and the list is to be sorted by telephone number, the list
must be able to contain duplicate entries, each with its own unique
telephone number.
Another example would be an application that needs to display an
ordered list of all members of a group. It would use this control
to create a result set of duplicate groupOfNames entries, each with
a single, unique value in its member attribute.
The key words "MUST", "SHOULD", and "MAY" used in this document
carry the meanings described in [Bradner97].
4. The Controls
Support for the controls is advertised by the presence of their OID
in the supportedControl attribute of a server's root DSE. The OID
for the request control is "2.16.840.1.113719.1.27.101.1" and the
OID for the response control is "2.16.840.1.113719.1.27.101.2".
4.1 Request Control
This control is included in the searchRequest message as part of the
controls field of the LDAPMessage, as defined in Section 4.1.12 of
[LDAPv3].
The controlType is set to "2.16.840.1.113719.1.27.101.1". The
criticality MAY be set to either TRUE or FALSE. The controlValue is
an OCTET STRING, whose value is the BER encoding of the following
type:
DuplicateEntryRequest ::= AttributeDescriptionList
The "AttributeDescriptionList" data type is described in 4.1.5 of
[LDAPv3] and describes a list of 0 or more AttributeDescription
types as also described in 4.1.5 of [LDAPv3]. Both definitions are
repeated here for convenience:
AttributeDescriptionList ::= SEQUENCE OF
AttributeDescription
AttributeDescription ::= <AttributeType> [ ";" <options> ]
While processing a search request, a server implementation examines
this list. If a specified attribute exists in an entry to be
returned by search, one instance of that entry per attribute value
is returned. In this case, the specified attribute in each entry
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LDAP Control for a Duplicate Entry Representation of Search Results
holds a single, unique value from the original set of values of that
attribute.
An AttributeDescription should only occur once in the list. If an
AttributeDescription is included in the DuplicateEntryRequest
multiple times, the server should return an unwillingToPerform error
in the DuplicateEntryResponse.
When two or more attribute types are specified by this control, the
number of duplicate entries is the combination of all values in each
attribute. Because of the potential complexity involved in servicing
multiple attribute types, server implementations MAY choose to
support a limited number of attribute types in the control.
There is a special case where either no attributes are specified, or
an attribute description value of "*" is specified. In this case,
all attributes are used. (The "*" allows the client to request all
user attributes in addition to specific operational attributes).
4.2 Response Control
This control is included in the searchResultDone message as part of
the controls field of the LDAPMessage, as defined in Section 4.1.12
of [LDAPv3].
The controlType is set to "2.16.840.1.113719.1.27.101.2". The
criticality is FALSE (MAY be absent). The controlValue is an OCTET
STRING, whose value is the BER encoding of the following SEQUENCE:
DuplicateEntryResponse ::= SEQUENCE {
result ENUMERATED {
success (0),
operations error (1), -- server internal failure
timeLimitExceeded (3), -- time limit reached before
-- attribute values could be
-- processed
sizeLimitExceeded (4), -- size limit reached as a
-- result of this control
adminLimitExceeded (11), -- result set too large for
-- server to handle
noSuchAttribute (16), -- unrecognized attribute
-- description
busy (51),
unwillingToPerform (53),
other (80) },
attributeType AttributeDescription OPTIONAL }
A result field is provided here to allow feedback in the case where
the criticality of the request control is FALSE, and the server
could not process the control - yet it could complete the search
operation successfully. If the request control's criticality is
TRUE, and the server cannot process the control, the resultCode of
the LDAPResult is used to report the error.
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LDAP Control for a Duplicate Entry Representation of Search Results
attributeType MAY be set to the value of the first attribute type
specified by the DuplicateEntryRequest that was in error. The
client MUST ignore the attributeType field if the result is success.
5. Protocol Examples
5.1 Simple example
This example will show this control being used to produce a list of
all telephone numbers in the "Acting" organizational unit of "Looney
Tunes". Let's say the following three entries exist in this
organization;
dn: cn=Bugs Bunny,ou=Acting,o=Looney Tunes
telephoneNumber: 555-0123
dn: cn=Daffy Duck,ou=Acting,o=Looney Tunes
telephoneNumber: 555-8854
telephoneNumber: 555-4588
telephoneNumber: 555-5884
dn: cn=Porky Pig,ou=Acting,o=Looney Tunes
telephoneNumber: 555-9425
telephoneNumber: 555-7992
First an LDAP search is specified with a baseDN of "ou=Acting,
o=Looney Tunes ", subtree scope, filter set to "telephoneNumber=*".
A DuplicateEntryRequest control is attached to the search,
specifying "telephoneNumber" as the attribute description, and the
search request is sent to the server.
The set of search results returned by the server would then consist
of the following entries:
dn: cn=Bugs Bunny,ou=Acting,o=Looney Tunes
telephoneNumber: 555-0123
dn: cn=Daffy Duck,ou=Acting,o=Looney Tunes
telephoneNumber: 555-8854
dn: cn=Daffy Duck,ou=Acting,o=Looney Tunes
telephoneNumber: 555-4588
dn: cn=Daffy Duck,ou=Acting,o=Looney Tunes
telephoneNumber: 555-5884
dn: cn=Porky Pig,ou=Acting,o=Looney Tunes
telephoneNumber: 555-9425
dn: cn=Porky Pig,ou=Acting,o=Looney Tunes
telephoneNumber: 555-7992
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LDAP Control for a Duplicate Entry Representation of Search Results
Note that it is not necessary to use an attribute type in this
control that is specified in the search filter. This example only
does so, because the result was to obtain a list of telephone
numbers.
5.2 Specifying multiple attributes
A more complicated example involving multiple attributes will result
in more entries. If we assume these entries in the directory:
dn: cn=Bugs Bunny,ou=Acting,o=Looney Tunes
givenName: Bugs
mail: bbunny@looneytunes.com
dn: cn=Elmer Fudd,ou=Acting,o=Looney Tunes
givenName: Elmer
givenName: Doc
mail: efudd@looneytunes.com
mail: bunnyhunter@nra.org
And both "mail" and "givenName" are specified as attribute types in
this control, the resulting set of entries would be this:
dn: cn=Bugs Bunny,ou=Acting,o=Looney Tunes
givenName: Bugs
mail: bbunny@looneytunes.com
dn: cn=Elmer Fudd,ou=Acting,o=Looney Tunes
givenName: Elmer
mail: efudd@looneytunes.com
dn: cn=Elmer Fudd,ou=Acting,o=Looney Tunes
givenName: Elmer
mail: bunnyhunter@nra.org
dn: cn=Elmer Fudd,ou=Acting,o=Looney Tunes
givenName: Doc
mail: efudd@looneytunes.com
dn: cn=Elmer Fudd,ou=Acting,o=Looney Tunes
givenName: Doc
mail: bunnyhunter@nra.org
5.3 Listing the members of a groupOfNames
This example shows how the controls can be used to turn a single
groupOfNames entry into multiple duplicate entries. Let<65>s say this
is our groupOfNames entry:
dn: cn=Administrators,o=acme
cn: Administrators
member: cn=aBaker,o=acme
member: cn=cDavis,o=acme
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LDAP Control for a Duplicate Entry Representation of Search Results
member: cn=bChilds,o=acme
member: cn=dEvans,o=acme
We could set our search base to "cn=Administrators,o=acme", filter
to "objectClass=*", use an object scope (to restrict it to this
entry) and send the duplicateEntryRequest control with "member" as
its attribute value. The resulting set would look like this:
dn: cn=Administrators,o=acme
member: cn=aBaker,o=acme
dn: cn=Administrators,o=acme
member: cn=cDavis,o=acme
dn: cn=Administrators,o=acme
member: cn=bChilds,o=acme
dn: cn=Administrators,o=acme
member: cn=dEvans,o=acme
This list can then be sorted by member and displayed (also by
member) in a list.
6 Relationship to other controls
This control is intended (but not limited) to be used with the
Server Side Sorting control [SSS]. By pairing this control with the
Server Side Sorting control, One can produce a set of entries,
sorted by attribute values, where each attribute value is
represented in the sorted set. Server implementations should ensure
that this control is processed before sorting the result of a
search, as this control alters the result set of search.
This control may also be used with the Virtual List View [VLV]
control (which has a dependency on the Server Side Sort control).
The nature of the dependency between the VLV control and the Sort
control is such that the Sorting takes place first. Because the sort
happens first, and because this control is processed before the sort
control, the impact of this control on the VLV control is minimal.
Some server implementations may need to carefully consider how to
handle the typedown functionality of the VLV control when paired
with this control. The details of this are heavily implementation
dependent and are beyond the scope of this document.
7. Notes for Implementers
Both client and server implementations should be aware that using
this control could potentially result in a very large set of search
results. Servers MAY return an adminLimitExceeded result in the
response control due to inordinate consumption of resources. This
may be due to some a priori knowledge such as a server restriction
of the number of attribute types in the request control that it's
Sermersheim Standards Track - Expires Sep 2000 Page 6
LDAP Control for a Duplicate Entry Representation of Search Results
willing to service, or it may be due to the server attempting to
service the control and running out of resources.
Client implementations must be aware that search entries returned,
when using this control will contain a subset of the values of any
specified attribute.
8. Acknowledgments
The author gratefully thanks the input and support of participants
of the LDAP-EXT working group.
9. References
[LDAPv3]
Wahl, M, S. Kille and T. Howes, "Lightweight Directory Access
Protocol (v3)", Internet Standard, December, 1997.
Available as RFC2251.
[SSS]
Wahl, M, A. Herron and T. Howes, "LDAP Control Extension for Server
Side Sorting of Search Results", Internet Draft, March, 1998.
Available as draft-ietf-ldapext-sorting-02.txt.
[VLV]
Boreham, D, Sermersheim, J, Anantha, A, Armijo, M, "LDAP Extensions
for Scrolling View Browsing of Search Results", Internet Draft,
June, 1999.
Available as draft-ietf-ldapext-ldapv3-vlv-03.txt.
[X.511]
ITU-T Rec. X.511, "The Directory: Abstract Service Definition",
1993.
[Bradner97]
Bradner, Scott, "Key Words for use in RFCs to Indicate Requirement
Levels", Internet Draft, March, 1997.
Available as RFC2119.
10. Author's Address
Jim Sermersheim
Novell, Inc.
122 East 1700 South
Provo, Utah 84606, USA
jimse@novell.com
+1 801 861-3088
Sermersheim Standards Track - Expires Sep 2000 Page 7
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