* @return <code>false</code> means that cancel failed, <code>true</code>
* that CancelWorkflowExecution was created.
*/
void cancelWorkflowExecution() {
Decision decision = new Decision();
CancelWorkflowExecutionDecisionAttributes cancel = new CancelWorkflowExecutionDecisionAttributes();
cancel.setDetails(null);
decision.setCancelWorkflowExecutionDecisionAttributes(cancel);
decision.setDecisionType(DecisionType.CancelWorkflowExecution.toString());
DecisionId decisionId = new DecisionId(DecisionTarget.SELF, null);
addDecision(decisionId, new CompleteWorkflowStateMachine(decisionId, decision));
}