1. A method for generating digital contents including a descriptor, the method comprising: defining a characteristic descriptor describing characteristics associated with the digital contents; defining first preference information associated with the characteristic descriptor, the first preference information indicating a relative priority of the characteristic descriptor; defining a usage environment descriptor describing a usage environment; defining second preference information associated with the usage environment descriptor, the second preference information indicating a relative priority of the usage environment descriptor; and generating digital contents including the characteristic descriptor, the usage environment descriptor and the first and second preference information.