有关于JBPM错误！

org.jbpm.api.JbpmException: expression 'Yes' in decision 'decision' returned unexisting outgoing transition name: Yes
org.jbpm.jpdl.internal.activity.DecisionExpressionActivity.execute(DecisionExpressionActivity.java:60)
org.jbpm.jpdl.internal.activity.DecisionExpressionActivity.execute(DecisionExpressionActivity.java:42)
org.jbpm.pvm.internal.model.op.ExecuteActivity.perform(ExecuteActivity.java:60)
org.jbpm.pvm.internal.model.ExecutionImpl.performAtomicOperationSync(ExecutionImpl.java:656)
org.jbpm.pvm.internal.model.ExecutionImpl.performAtomicOperation(ExecutionImpl.java:616)
org.jbpm.pvm.internal.model.ExecutionImpl.start(ExecutionImpl.java:217)
org.jbpm.pvm.internal.cmd.StartProcessInstanceInLatestCmd.execute(StartProcessInstanceInLatestCmd.java:65)
org.jbpm.pvm.internal.cmd.StartProcessInstanceInLatestCmd.execute(StartProcessInstanceInLatestCmd.java:38)
org.jbpm.pvm.internal.svc.DefaultCommandService.execute(DefaultCommandService.java:42)
org.jbpm.pvm.internal.tx.StandardTransactionInterceptor.execute(StandardTransactionInterceptor.java:54)
org.jbpm.pvm.internal.svc.EnvironmentInterceptor.executeInNewEnvironment(EnvironmentInterceptor.java:53)
org.jbpm.pvm.internal.svc.EnvironmentInterceptor.execute(EnvironmentInterceptor.java:40)
org.jbpm.pvm.internal.svc.RetryInterceptor.execute(RetryInterceptor.java:55)
org.jbpm.pvm.internal.svc.SkipInterceptor.execute(SkipInterceptor.java:43)
org.jbpm.pvm.internal.svc.ExecutionServiceImpl.startProcessInstanceByKey(ExecutionServiceImpl.java:66)
svt.ProcessVariables.doGet(ProcessVariables.java:47)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)