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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.
1. LDAP Search Filter Definition
An LDAP 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, lessOrEqual [6] AttributeValueAssertion, present [7] AttributeType, approxMatch [8] AttributeValueAssertion }
SubstringFilter ::= SEQUENCE { type AttributeType, SEQUENCE OF CHOICE { initial [0] LDAPString, any [1] LDAPString, final [2] LDAPString } }
where the LDAPString above is limited to the IA5 character set. The AttributeType is a string representation of the attribute object identifier in dotted OID format (e.g., "2.5.4.10"), or the shorter string name of the attribute (e.g., "organizationName", or "o"). 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 [1].
2. String Search Filter Definition
The string representation of an LDAP search filter is defined by the following BNF. It uses a prefix format.
<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 ')', these characters
should be escaped by preceding them with the backslash '/' character.
3. Examples
This section gives a few examples of search filters written using this notation.
[1] Yeong, W., Howes, T., and S. Kille, "Lightweight Directory Access Protocol", RFC1487, Performance Systems International, University of Michigan, ISODE Consortium, July 1993.
[2] Howes, T., Kille, S., Yeong, W., and C. Robbins, "The String Representation of Standard Attribute Syntaxes", RFC1488, University of Michigan, ISODE Consortium, Performance Systems International, NeXor Ltd., July 1993.
[3] "Specification of Basic Encoding Rules for Abstract Syntax Notation One (ASN.1)", CCITT Recommendation X.209, 1988.
6. Author's Address
Tim Howes University of Michigan ITD Research Systems 535 W William St. Ann Arbor, MI 48103-4943 USA
