I have found this:
....you can use the following snippet of code to convert the brl to a drl rule:
BRXMLPersitence read = BRXMLPersitence.getInstance();
BRDRLPersistence write = BRDRLPersistence.getInstance();
String brl = ... read from the .brl file as needed...
String outputDRL = write.marshall(read.unmarshal(brl));
//then pass the outputDRL to the PackageBuilder as normal
Can you explain please: "String brl = ... read from the .brl file as needed..."
for example if I have  "first.brl" and I want "first.drl"
Thank you...