1. A device for generating presentation data comprising: a document data acquisition part for acquiring a plurality of document data sets, each document data set containing contents to be presented; a transformation data acquisition part for acquiring a plurality of transformation data sets, each transformation data set defining a rule for transforming respective one of said document data sets into a presentation data set that presents contents of said document data sets; a layout data acquisition part for acquiring a layout data set containing layout information that defines a layout of said document data sets upon presenting contents of said document data sets; and a presentation data-generating part for transforming said document data sets based on said layout data set and on said transformation data sets so as to generate a unified presentation data set that presents contents of said document data sets in accordance with said layout defined in said layout data set.