1. A deployment method for deploying a new virtual appliance on a data processing center including one or more computers configured to each host one or more virtual machines, the new virtual appliance including one or more new virtual machines which each include one or more new software programs, wherein the deployment method includes steps comprising: determining structure information of the new virtual appliance, the structure information of the new virtual appliance including an indication of the one or more new virtual machines and an indication of the one or more new software programs; retrieving configuration information indicative of a current configuration of the data processing center; retrieving license condition information indicative of license conditions applicable to the data processing center; determining a deployment scheme of the virtual appliance on the data processing center, the determination of the deployment scheme being performed by optimizing a cost function based on the license condition information, the configuration information and the structure information; and deploying the new virtual appliance according to the deployment scheme.