Disclosed herein is a data processing apparatus that sets identification information for identifying each of a plurality of contents based on metadata added to each of the contents. The apparatus includes: title information acquisition means for acquiring title information of each of the contents, the title information concerning a title of the content and being included in the metadata; information extraction means for comparing the title information of each of the contents to extract a part of the title information that is common to all of the contents; and identification information setting means for setting the identification information of each of the contents based on the other part of the title information than the part of the title information that is common to all of the contents.