A simulation apparatus according to one embodiment, including: an event receiver, a decision maker and an execution command transmitter. The event receiver receives an event showing a situation of a first monitor target simulated by a first simulator simulating at least one of motion and state change of the first monitor target from a monitor apparatus monitoring a simulation of the first simulator. The decision maker determines an action based on the event, the action to be carried out with respect to a second monitor target undergoing a simulation of at least one of motion and state change by a second simulator synchronized with the first simulator by time progress. The execution command transmitter transmits an execution command of the action determined by the decision maker to a control apparatus controlling the second simulator.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A simulation apparatus comprising: an event receiver receiving an event showing a situation of a first monitor target simulated by a first simulator simulating at least one of motion and state change of the first monitor target from a monitor apparatus monitoring a simulation of the first simulator; a decision maker determining an action based on the event, the action to be carried out with respect to a second monitor target undergoing a simulation of at least one of motion and state change by a second simulator synchronized with the first simulator by time progress; and an execution command transmitter transmitting an execution command of the action determined by the decision maker to a control apparatus controlling the second simulator. 2. The simulation apparatus according to claim 1, wherein the decision maker determines, based on at least one of a type of the event and a value of the event, the action to change an acquisition frequency of the event about the first monitor target; and the execution command transmitter transmits an execution command of the action determined by the decision maker to a control apparatus controlling the first simulator. 3. The simulation apparatus according to claim 2, wherein based on the value of the event and a value of an event received before the event by the event receiver, the decision maker determines the action to change the acquisition frequency of the event about the first monitor target. 4. The simulation apparatus according to claim 1, wherein the first simulator simulates at least one of the motion and state change of the plurality of first monitor targets; an agent including the event receiver, the decision maker, and the execution command transmitter is provided for each of the first monitor targets; and the agent receives the event showing the situation of the first monitor target corresponding to the agent from the monitor apparatus. 5. The simulation apparatus according to claim 4, wherein the decision maker has a plurality of control rules determining types of events, conditions based on values of the events, and actions to be executed, selects the control rule matching a type of the received event and satisfying the condition from among the plurality of control rules, and determines the action shown in the selected control rule. 6. The simulation apparatus according to claim 4, wherein the decision maker of at least one of the agents reports the event to a user device via wired or wireless communication and determines the action to be executed in accordance with an input of an instruction signal from the user. 7. The simulation apparatus according to claim 6, wherein the execution command transmitter transmits a control command to the user device based on the execution command. 8. The simulation apparatus according to claim 1, further comprising: a simulation controller synchronizing the time progress of the first and second simulators by transmitting an instruction signal to advance the simulations of the first simulator and the second simulator by certain time to the control apparatuses controlling the first and second simulators, respectively, and, when both of the first and second simulators are advanced by the certain time, repeatedly transmitting the next instruction signal to advance the certain time. 9. The simulation apparatus according to claim 2, further comprising: the monitor apparatus, a first control apparatus controlling the first simulator, and a second control apparatus controlling the second simulator; wherein the first control apparatus transmits an instruction signal to the monitor apparatus, the instruction signal to acquire an event about the first monitor target at an acquisition frequency in accordance with the execution command of the action; the monitor apparatus acquires the event in accordance with the acquisition frequency shown by the instruction signal and transmits the event to the event receiver; and the second control apparatus controls at least one of motion and state of the second monitor target in accordance with the execution command of the action. 10. The simulation apparatus according to claim 1, further comprising a trigger event reporter periodically generating a trigger event about the second simulator; wherein the event receiver receives the trigger event generated by the trigger event reporter; the decision maker determines execution of the action about the second monitor target in accordance with the number of times of reception of the trigger event by the event receiver; and the execution command transmitter transmits the execution command of the action to the control apparatus controlling the second simulator. 11. The simulation apparatus according to claim 1, further comprising: a trigger event reporter periodically generating a trigger event about the first simulator; wherein the event receiver receives the trigger event generated by the trigger event reporter; the decision maker makes a decision to acquire an event about the first monitor target in accordance with the number of reception of the trigger event by the event receiver; and the execution command transmitter transmits an execution command of an action to acquire the event to the control apparatus controlling the first simulator. 12. The simulation apparatus according to claim 1, wherein the event receiver receives an event from a monitor apparatus monitoring a simulation of the second simulator, the event showing a situation of the second monitor target simulated by the second simulator; based on the event received by the event receiver, the decision maker determines an action to be carried out with respect to the first monitor target simulated by the first simulator; and the execution command transmitter transmits an execution command of an action determined by the decision maker to a control apparatus controlling the first simulator. 13. The simulation apparatus according to claim 1, wherein the first monitor target is a vehicle; and a value of the event expresses at least one of a velocity of the vehicle, a position of the vehicle, and the number of another vehicle(s) present around the vehicle. 14. The simulation apparatus according to claim 1, wherein the first monitor target is an apparatus consuming electric power; and a value of the event expresses at least one of a voltage, a current, electric power, and an electric power usage amount of the apparatus consuming the electric power. 15. The simulation apparatus according to claim 1, wherein the first monitor target is a vehicle moving by using energy; and a value of the event expresses an energy remaining amount of the vehicle. 16. The simulation apparatus according to claim 1, wherein the first monitor target is a provider of a product or a service; and a value of the event expresses a price of the product or the service provided by the provider. 17. The simulation apparatus according to claim 1, further comprising: a communicator connected to the first monitor target and communicatable with a wired or wireless network; wherein the monitor apparatus monitors at least one of the motion and state change of the first monitor target of the network by using the communicator instead of the first monitor target simulated by the first simulator; the event receiver receives an event showing a situation of the first monitor target of the network from the monitor apparatus; based on the event received by the event receiver, the decision maker determines the action with respect to the second monitor target simulated by the second simulator undergoing synchronization of time progress with the network; and the execution command transmitter transmits an execution command of the action determined by the decision maker to the control apparatus controlling the second simulator. 18. The simulation apparatus according to claim 1, further comprising: a communicator connected to the second target and communicatable with a wired or wireless network; wherein the first simulator is undergoing synchronization of time progress with the network; the decision maker determines an action to be carried out with respect to the second monitor target connected to the network instead of the second monitor target simulated by the second simulator; and the execution command transmitter transmits an execution command of the action determined by the decision maker to the second monitor target connected to the network via the communicator. 19. A simulation method performed by a computer, comprising: receiving an event showing a situation of a first monitor target simulated by a first simulator simulating at least one of motion and state change of the first monitor target from a monitor apparatus monitoring a simulation of the first simulator; determining an action based on the event, the action to be carried out with respect to a second monitor target undergoing a simulation of at least one of motion and state change by a second simulator synchronized with the first simulator by time progress; and transmitting an execution command of the action to a control apparatus controlling the second simulator. 20. A non-transitory computer readable medium having instructions stored therein which, when executed by a computer, cause a computer to perform operations comprising: receiving an event showing a situation of a first monitor target simulated by a first simulator simulating at least one of motion and state change of the first monitor target from a monitor apparatus monitoring a simulation of the first simulator; determining an action based on the event, the action to be carried out with respect to a second monitor target undergoing a simulation of at least one of motion and state change by a second simulator synchronized with the first simulator by time progress; and transmitting an execution command of the action to a control apparatus controlling the second simulator.