1. An information processing apparatus, comprising: an input unit configured to receive content in a form of an audio/video signal including closed captioning information; an extraction unit configured to extract sequentially in time keywords from multiple character strings included in the closed captioning information; a processor configured to calculate similarity values of the extracted keywords included in adjacent first regions of the multiple character strings, each first region including a predefined part of the multiple character strings; a detection window setting unit configured to set the adjacent first regions encompassing the extracted keywords, and to shift the adjacent first regions by a keyword one by one; a detection unit configured to detect a boundary point in the content of the audio/video signal based on the calculated similarity values, wherein the boundary point defines a separation between a portion of the audio/video signal defining a first topic of the content and another portion of the audio/video signal defining a second topic of the content; an attribute information generation unit configured to generate attribute information to be associated with the boundary point indicating a location of the boundary point within the content, and to add the attribute information indicating the location of the boundary point to the content, wherein the attribute information associated with the boundary point is one of time information, title information, and topic information; a memory device configured to store the content including the added attribute information; and a reproducing unit configured to reproduce the content including the added attribute information, wherein the reproducing unit is configured to search through the content to reproduce subparts of the content starting at a location of the boundary point identified by the attribute information, and the reproducing unit is configured to generate a window on a display in which an image of where the boundary point is located within the content is thumbnail-displayed.