MMS uses built-in rules when you omit the action line or the source, or both, from a dependency rule. Built-in rules allow MMS to assume dependencies that are not stated in the description file and to perform actions necessary to update the target. To decide which built-in rule to apply to a dependency, MMS also uses the suffixes precedence list. Built-in rules also allow you to access files stored in OpenVMS, CMS, FMS libraries and records stored in the Common Data Dictionary.