An information processing device that attaches common accompanying data to a content group composed of contents. The information processing device acquires the contents, acquires one or more characteristics of each acquired content and searches among reference data items in order to acquire one or more reference data items that each include any of the one or more characteristics, each reference data item having attached thereto at least one attribute used for identifying the reference data item, the reference data items being data other than the contents. The information processing device then specifies, among the attributes attached to the acquired one or more reference data items, an attribute that also pertains to the contents, uses the specified attribute as an attribute for identifying each of the contents, and attaches the specified attribute to each of the contents.