A management system, comprising: a management device (EMS 160), and an equipment (130, 150), wherein the management device (EMS 160) is configured to be connected to the equipment (130, 150) provided in a facility via a network provided in the facility, the management device (EMS 160) comprising: a transmitter configured to transmit a first command to the equipment (130, 150) to instruct an operation of the equipment (130, 150), wherein a property included in the first command includes a variable property indicating a variable that can be changed by the operation of the equipment(130, 150); the equipment (130, 150) comprising: a controller configured to control the equipment (130, 150) to start an operation of the equipment (130, 150) instructed by the first command, a transmitter configured to transmit a response command to the management device (EMS 160), the response command containing a specific value as the variable property to specify whether the operation is performed according to the first command, characterized in that the controller is further configured to keep a variable, indicated by the variable property, without change when the operation instructed by the first command is ongoing; and wherein the specific value is a different value from a value indicated by the variable property contained in the first command. a management device (EMS 160), and an equipment (130, 150), wherein the management device (EMS 160) is configured to be connected to the equipment (130, 150) provided in a facility via a network provided in the facility, the management device (EMS 160) comprising: a transmitter configured to transmit a first command to the equipment (130, 150) to instruct an operation of the equipment (130, 150), wherein a property included in the first command includes a variable property indicating a variable that can be changed by the operation of the equipment(130, 150); the equipment (130, 150) comprising: a controller configured to control the equipment (130, 150) to start an operation of the equipment (130, 150) instructed by the first command, a transmitter configured to transmit a response command to the management device (EMS 160), the response command containing a specific value as the variable property to specify whether the operation is performed according to the first command, characterized in that the controller is further configured to keep a variable, indicated by the variable property, without change when the operation instructed by the first command is ongoing; and wherein the specific value is a different value from a value indicated by the variable property contained in the first command. a transmitter configured to transmit a first command to the equipment (130, 150) to instruct an operation of the equipment (130, 150), wherein a property included in the first command includes a variable property indicating a variable that can be changed by the operation of the equipment(130, 150); the equipment (130, 150) comprising: a controller configured to control the equipment (130, 150) to start an operation of the equipment (130, 150) instructed by the first command, a transmitter configured to transmit a response command to the management device (EMS 160), the response command containing a specific value as the variable property to specify whether the operation is performed according to the first command, characterized in that the controller is further configured to keep a variable, indicated by the variable property, without change when the operation instructed by the first command is ongoing; and wherein the specific value is a different value from a value indicated by the variable property contained in the first command. a controller configured to control the equipment (130, 150) to start an operation of the equipment (130, 150) instructed by the first command, a transmitter configured to transmit a response command to the management device (EMS 160), the response command containing a specific value as the variable property to specify whether the operation is performed according to the first command, characterized in that the controller is further configured to keep a variable, indicated by the variable property, without change when the operation instructed by the first command is ongoing; and wherein the specific value is a different value from a value indicated by the variable property contained in the first command.