A mediascape comprises media items and related action-triggers each specifying a condition set of one or more conditions, and at least one media-item-specific action that is to be triggered upon satisfaction of the condition set. During authoring (31) at least one action-trigger is specified with a location-based condition that has a customizable parameter; thereafter, the mediascape is released to a third party (34) with an indication that it contains a customizable parameter. The customizable parameter is then customized (38) in accordance with input from the third party (34) and the customized mediascape (39) is deployed to users for use.