Customizing the jBPM hibernate mapping files
To customize any of the jBPM hibernate mapping files, you can proceed as 
      follows:
    
- copy the jBPM hibernate mapping file(s) you want to copy from the 
        sources (src/jbpm-jpdl-sources.jar)
- 
        put the copy anywhere you want on the classpath, but make sure it is not 
        the exact same location as they were before.
      
- 
        update the references to the customized mapping files in the hibernate.cfg.xml 
        configuration file