There is a standard Rat XSD file that describes the configuration file options and can be used to verify any configuration file that only depends on the matchers shipped with Rat.
If new matchers are implemented and properly documented the system can generate the XSD for it as well. To generate a XSD execute the following:
java -jar apache-rat/target/apache-rat-0.17-SNAPSHOT.jar org.apache.rat.tools.xsd.XsdGenerator [options]
Where '[options]' are the options used to add the new definitions to Rat. Specifically these will include configurations that define new matchers.