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Network Working Group                                        Tim Howes
INTERNET DRAFT                            Netscape Communications Corp.
OBSOLETES: RFC 1960                                      October, 1996
Expire in six months

             A String Representation of LDAP Search Filters

1.  Status of this Memo

This document is an Internet-Draft.  Internet-Drafts are  working  docu-
ments  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.''

To learn the current status of  any  Internet-Draft,  please  check  the
``1id-abstracts.txt''  listing  contained in the Internet- Drafts Shadow
Directories on ds.internic.net (US East Coast), nic.nordu.net  (Europe),
ftp.isi.edu (US West Coast), or munnari.oz.au (Pacific Rim).

2.  Abstract

The Lightweight Directory Access Protocol (LDAP) [1] defines  a  network
representation  of  a search filter transmitted to an LDAP server.  Some
applications may find it useful to have a  common  way  of  representing
these  search filters in a human-readable form.  This document defines a
human-readable string format for representing LDAP search filters.

This document replaces RFC 1960, extending the string LDAP filter defin-
ition to include support for LDAP version 3 extended match filters.

3.  LDAP Search Filter Definition

An LDAPv3 search filter is defined in [1] as follows:

     Filter ::= CHOICE {
             and                [0] SET OF Filter,
             or                 [1] SET OF Filter,
             not                [2] Filter,
             equalityMatch      [3] AttributeValueAssertion,
             substrings         [4] SubstringFilter,
             greaterOrEqual     [5] AttributeValueAssertion,

Howes                                                           [Page 1]

INTERNET DRAFT                                              October 1996

             lessOrEqual        [6] AttributeValueAssertion,
             present            [7] AttributeType,
             approxMatch        [8] AttributeValueAssertion,
             extensibleMatch    [9] MatchingRuleAssertion

     SubstringFilter ::= SEQUENCE {
             type    AttributeType,
             SEQUENCE OF CHOICE {
                     initial        [0] LDAPString,
                     any            [1] LDAPString,
                     final          [2] LDAPString

     AttributeValueAssertion ::= SEQUENCE {
             attributeType   AttributeType,
             attributeValue  AttributeValue

     MatchingRuleAssertion ::= SEQUENCE {
             matchingRule    [1] MatchingRuleID OPTIONAL,
             type            [2] AttributeType OPTIONAL,
             matchValue      [3] AssertionValue,
             dnAttributes    [4] BOOLEAN DEFAULT FALSE

     AttributeType ::= LDAPString

     AttributeValue ::= OCTET STRING

     MatchingRuleID ::= LDAPString

     LDAPString ::= OCTET STRING

where the LDAPString above is limited to the  IA5  character  set.   The
AttributeType  is a string representation of the attribute type name and
is defined in [1].  The AttributeValue OCTET STRING has the form defined
in [2].  The Filter is encoded for transmission over a network using the
Basic Encoding Rules defined in [3], with simplifications  described  in

4.  String Search Filter Definition

The string representation of an LDAP search filter  is  defined  by  the
following grammar.  It uses a prefix format.

     <filter> ::= '(' <filtercomp> ')'

Howes                                                           [Page 2]

INTERNET DRAFT                                              October 1996

     <filtercomp> ::= <and> | <or> | <not> | <item>
     <and> ::= '&' <filterlist>
     <or> ::= '|' <filterlist>
     <not> ::= '!' <filter>
     <filterlist> ::= <filter> | <filter> <filterlist>
     <item> ::= <simple> | <present> | <substring> | <extensible>
     <simple> ::= <attr> <filtertype> <value>
     <filtertype> ::= <equal> | <approx> | <greater> | <less>
     <equal> ::= '='
     <approx> ::= '~='
     <greater> ::= '>='
     <less> ::= '<='
     <extensible> ::= ( NULL | <attr> ) [ ':dn' ] [ ':' <matchingrule> ]
                             ':=' <value>
     <matchingrule> ::= <matchingrulename> | <oid>
     <present> ::= <attr> '=*'
     <substring> ::= <attr> '=' <initial> <any> <final>
     <initial> ::= NULL | <value>
     <any> ::= '*' <starval>
     <starval> ::= NULL | <value> '*' <starval>
     <final> ::= NULL | <value>

<attr> is a string representing an AttributeType,  and  has  the  format
defined  in [1].  <value> is a string representing an AttributeValue, or
part of one, and has the form defined in [2].  If a <value> must contain
one  of the characters '*' or '(' or ')' or '\', these characters should
be escaped by preceding them with the  backslash  '\'  character.   Note
that although both the <substring> and <present> productions can produce
the 'attr=*' construct, this construct is used only to denote a presence

<oid> is a dotted string representation of an object  identifier  (e.g.,
"")  identifying  a  matching rule to use when comparing <value>.
<matchingrulename> is a name given to a matching  rule,  as  defined  in
[2].  One  of  <attr>  or <matchingrule> is required in the <extensible>

5.  Examples

This section gives a few examples of search filters written  using  this

     (cn=Babs Jensen)
     (!(cn=Tim Howes))
     (&(objectClass=Person)(|(sn=Jensen)(cn=Babs J*)))
     (o=Parentheses r all your parenthetical needs))

Howes                                                           [Page 3]

INTERNET DRAFT                                              October 1996

The following two examples illustrate the use of extensible matching.

     (cn: Flintstone)
     (sn:dn: Rubble)
     (o:dn:=Ace Industry)

The second example illustrates the use of the ":dn" notation to indicate
that  matching rule "" should be used when making comparisons,
and that the attributes of an entry's distinguished name should be  con-
sidered part of the entry when evaluating the match.

The third example denotes an equality match, except that  DN  components
should be considered part of the entry when doing the match.

6.  Security Considerations

Security considerations are not discussed in this document.

7.  Bibliography

[1]  Lightweight Directory Access Protocol (v3), M. Wahl, T.  Howes,  S.
     Kille,   Internet   Draft   draft-ietf-asid-ldapv3-protocol-03.txt,
     October 1996.

[2]  Lightweight Directory Access Protocol: Standard and Pilot Attribute
     Definitions,  M.  Wahl,  A.  Coulbeck, T. Howes, S. Kille, Internet
     Draft draft-ietf-asid-ldapv3-attributes-03.txt, October 1996.

[3]  Specification of Basic Encoding Rules for Abstract Syntax  Notation
     One (ASN.1).  CCITT Recommendation X.209, 1988.

8.  Author's Address

   Tim Howes
   Netscape Communications Corp.
   501 E. Middlefield Road
   Mountain View, CA 94043
   +1 415 937-3419

Howes                                                           [Page 4]

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