public void relateAcrossR689To(Value_c target, boolean notifyChanges) {
    if (target == null) return;

    if (target == WritesValue) return; // already related

    if (WritesValue != target) {

      Object oldKey = getInstanceKey();

      if (WritesValue != null) {

        WritesValue.clearBackPointerR689To(this);

        if (Boolean.valueOf(System.getenv("PTC_MCC_ENABLED")) == true) { // $NON-NLS-1$
          Ooaofooa.log.println(
              ILogger.CONSISTENCY,
              "AssignToMember_c.relateAcrossR689To(Value_c target)",
              "Relate performed across R689 from Assign to Member to Value without unrelate of prior instance.");
        }
      }

      WritesValue = target;
      m_l_value_id = target.getValue_id();
      updateInstanceKey(oldKey, getInstanceKey());
      target.setBackPointerR689To(this);
      target.addRef();
    }
  }
  public void unrelateAcrossR689From(Value_c target, boolean notifyChanges) {
    if (target == null) return;

    if (WritesValue == null) return; // already unrelated

    if (target != WritesValue) {
      Exception e = new Exception();
      e.fillInStackTrace();
      CorePlugin.logError("Tried to unrelate from non-related instance across R689", e);
      return;
    }

    if (target != null) {
      target.clearBackPointerR689To(this);
    }

    if (WritesValue != null) {

      m_l_value_id = WritesValue.getValue_id();
      WritesValue = null;
      target.removeRef();
    }
  }