*/
public static WfAssignment getWfAssignment(WfActivity activity, WfResource resource, Timestamp fromDate, boolean create) throws WfException {
if (activity == null) throw new WfException("WfActivity cannot be null");
if (resource == null) throw new WfException("WfResource cannot be null");
if (fromDate == null) fromDate = new Timestamp(new Date().getTime());
return new WfAssignmentImpl(activity, resource, fromDate, create);
}