A search system interface is described. Known search system interfaces are largely unable to find composite articles on the basis of a description of the distribution of content types within them. A problem with providing such a search interface is the laboriousness of generating a suitable query. To address this problem, a display is provided with a key showing content types and associated map symbols. Also provided on the display is a search mapping area, which takes advantage of the fact that parts of text documents, and many other types of searchable items, can be referenced by one or more ordinal values, by having an easily perceivable relationship between position in the search mapping area and position within a target document. By operating the device to offer a digital painting interface such that the user can paint parts of the search mapping area in a visual style associated with the content type the user hopes to find in the corresponding part of the text document, the user is able to rapidly and intuitively provide the search system with a description of how content types would be distributed in documents he wishes to find. The search system interface can similarly be used to specify a desired composition of articles belonging to different categories over a period of time.