| CPC G06Q 20/3825 (2013.01) [G06F 16/27 (2019.01)] | 10 Claims |

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1. A control method executed by a device out of a plurality of devices in a contract management system that includes the plurality of devices, the plurality of devices are directly or indirectly connected to a network in a manner that the plurality of devices can communicate with one another via the network, the control method comprising:
obtaining first transaction data that includes a first variable and a second variable, the first variable indicating first information on a first contract made between a first user and a second user, the second variable indicating second information different from the first information on the first contract and being set to a predetermined value indicating that the second information is undetermined;
storing the first transaction data obtained into a distributed ledger;
executing storing processing of reading out the second variable included in the first transaction data stored in the distributed ledger, and storing the second variable into a storage included in the device, the storage being rewritable, the storage also being separate from the distributed ledger;
obtaining second transaction data that includes a third variable and a change command, the third variable indicating third information on a second contract made between the first user and a third user, the change command being a command for changing the second variable, based on the third variable;
storing the second transaction data obtained into the distributed ledger; and executing change processing of changing, according to the change command, the second variable stored in the storage from the predetermined value, after the second transaction data is stored into the distributed ledger,
wherein the first contract includes a contract that stipulates that the first user is to purchase material from the second user, and the material purchased is to be delivered to a delivery destination,
the first information includes a purchase price of the material and a deadline for delivering the material,
the second information includes the delivery destination of the material,
the second contract includes a contract that stipulates that the third user is to manufacture a product from the material delivered from the second user, and deliver the product to the first user, and
the third information includes a purchase price of the product, a deadline for delivering the product, and a delivery destination of the product.
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