Matching rule uses can be specified with existing schema components and don't require additional code for implementation.

The following formal specification for attribute types is provided in RFC 4512, section 4.1.4.

MatchingRuleUseDescription = "(" wsp
numericoid                  ; Object identifier 
[ sp "NAME" sp qdescrs ]    ; Short name descriptor 
[ sp "DESC" sp qdstring ]   ; Description 
[ sp "OBSOLETE" ]           ; Specifies if the rule use is inactive 
sp "APPLIES" sp oid         ; Attribute types 
extensions wsp ")"          ; Extensions followed by a white space and ")"

The following extensions are specific to the PingDirectory server and aren't defined in RFC 4512.

extensions = / 
"X-SCHEMA-FILE" /        ; Specifies which schema file contains the definition
"X-READ-ONLY"            ; True or False. Specifies if the file that contains 
                         ;   the schema element is marked as read-only in the
                         ;   server configuration.