Another easy one but this is really useful when you need to string various rule files together. Just modify this to meet your needs:
import yourrulefile : "yourrulefile.cga"
Lot-->
10% : yourrulefile //this calls the rule file specified above
90% : another // change this to whatever you want perhaps another rule file?
else : NIL // change this to whatever you want perhaps another rule file?
another--> color("#000000")