APPROXIMATE is a Matching Rule used to indicate that a filter should match an entry only if the entry contains at least one value for the specified attribute that is approximately equal to the provided Attribute Value Assertion.

The definition of "approximately equal to" may vary from one LDAP Server Implementation to another, and from one attribute to another, but it is often implemented as a "sounds like" match using a variant of the metaphone or double-metaphone algorithm. An approximate-match filter contains only an attribute name and an Attribute Value Assertion.

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