Commonly Used Matching Rules

There are a number of matching rules defined in LDAP, both in the core protocol specification as well as in other related RFCs and Internet Drafts. Many of these matching rules are defined in RFC 4517 (LDAP Syntaxes and Matching Rules), in section 4.2. Some of the most commonly used matching rules include:

caseIgnoreMatch, caseIgnoreOrderingMatch, caseIgnoreSubstringsMatch

These are equality, ordering, and substring matching rules, respectively, that ignore differences in capitalization and also treat multiple consecutive spaces as a single space.

caseExactMatch, caseExactOrderingMatch, caseExactSubstringsMatch

These are equality, ordering, and substring matching rules, respectively, that treat values in a case-sensitive manner but do treat multiple consecutive spaces as a single space.

octetStringMatch, octetStringOrderingMatch, octetStringSubstringsMatch

These are equality, ordering, and substring matching rules, respectively, that perform byte-for-byte comparisons of the values, treating them as binary data rather than strings.

numericStringMatch, numericStringOrderingMatch, numericStringSubstringsMatch

These are equality, ordering, and substring matching rules, respectively, that operate on values that start with a numeric digit, and contain only numeric digits and spaces. Spaces are ignored when performing matching with these matching rules.

distinguishedNameMatch

This is an equality matching rule that operates on distinguished name (DN) values. It ignores spaces around the commas or semicolons that separate DN components, spaces around plus signs that separate RDN components, and spaces around equal signs that separate RDN attribute type names from their corresponding values. Differences in capitalization are ignored for attribute type names. Equality matching for attribute values is performed using the equality matching rule for the corresponding attribute type.

doubleMetaphoneApproximateMatch

This is an approximate matching rule that uses the double metaphone algorithm to perform a “sounds like” comparison. Note that this matching rule is not part of any official LDAP specification, but it is included in the directory server for added flexibility.