Manufacturer-specific-service-extension-definition {itu-t recommendation 
  h 450 1 version2(1) msi-definition(18)} DEFINITIONS AUTOMATIC TAGS ::=
BEGIN

EXTENSION ::= CLASS {&ArgumentType  ,
                     &extensionId   OBJECT IDENTIFIER
}WITH SYNTAX {ARGUMENT &ArgumentType
              IDENTIFIER &extensionId
}

Extension{EXTENSION:ExtensionSet} ::= SEQUENCE {
  extensionId        EXTENSION.&extensionId({ExtensionSet}),
  extensionArgument  EXTENSION.&ArgumentType({ExtensionSet}{@extensionId})
}

-- ExtensionSet is a set of objects of class EXTENSION.
-- Actual values of ExtensionSet are defined by the individual manufacturers. 
-- Element extensionId is constrained to be the identifier of an object from that set.
-- Element extensionArgument is constrained to be the argument type for that particular
-- object.
END -- of Manufacturer-specific-service-extension-definition