A physical object is provided that comprises a base medium, such as a paper sheet, and multiple memory tags embedded in it or attached to it. At least one of the memory tags stores location data concerning a location relationship between the object and one or more of the tags. The location data can comprise, for example, tag-location data giving the location in or on the object of the or each tag concerned, or area-of-responsibility data indicating the area of the object's surface for which the or each tag concerned has responsibility in terms of storing related data items such as print data items. Apparatus is provided for writing the location data; apparatus is also provided for subsequently using and displaying the location data particularly for facilitating access to data items stored by the tags.