[rules-users] use rule assign actor

hi , i am a drools flow newbie.I want to using "assignment rule" assign a actor to a HumanTask. I have write a dsl and dslr files and following code : kbuilder.add(ResourceFactory.newClassPathResource("HelloWorldSample.rf"), ResourceType.DRF); kbuilder.add(ResourceFactory.newClassPathResource("assignment.dsl"), ResourceType.DSL); kbuilder.add(ResourceFactory.newClassPathResource("assignment.dslr"), ResourceType.DSLR); but when i start a process instance and the token arrive at a humantask,the "assignment rule" couldn't be firing. who can tell me how can i do it?