The employees' union and the management at Rexen Inc. enter into a contract, which requires Rexen to improve its facilities and to ensure the safety of its employees. However, a few months later, the employees observe that the conditions have remained the same and that management has not taken any steps to revamp its systems. As a result, the union files a case against Rexen for violating the terms of their contract. In order to resolve this issue, the union and Rexen will both have to participate in a process for resolving conflicts, known as _____.