of the document contents is deleted when a distance of the one of the document contents in the feature amount space is equal to or greater than the threshold value set in advance therefore by indicating the document content from which the attribute information 112 a has been deleted it can be presented to the user that the attribute information 112 a added to the document content is incorrect in addition when there is a document content having a distance in the feature amount space equal to or greater than the threshold value set in advance the user is notified of the presence of such document content therefore it is possible to present information allowing the user to determine whether or not the attribute information 112 a added to the document content is correct when there is a document content having a distance in the feature amount space equal to or greater than the threshold value set in advance the attribute information of the document content is added again therefore by indicating the document content to which the attribute information has been added again it can be presented to the user that the attribute information 112 a added to the document content is incorrect in short according to the embodiment described above it is possible to present information allowing the user to determine whether or not the attribute information 112 a added to the document contents is correct in addition in the present embodiment when there is a document content having a distance equal to or greater than the threshold value set in advance the attribute information is deleted and the user is notified of the situation or.