Drop zones: an extension to LiveDoc

LiveDoc [6] is an extension to the Macintosh user experience that allows documents to reveal structured information in such a way that it can be readily identified and used to achieve specific actions. Various kinds of recognizers, including contextfree grammars, are used to describe the structures to be found; these structures can be made up of either a single lexical term (either a variable structure like a phone number, or a collection of static strings, like company names) or multiple terms (for instance, a meeting can be defined as a combination of date, time, and venue structures). Small pieces of code can then be associated with each structure to instruct applications to carry out specific user actions on the discovered structuresperhaps to tell a telephony application to "Dial this phone number." These actions can then be offered to users by visually highlighting the discovered structures and attaching pop-up menus to the highlights. (See also [7] for an alternate interface formalism implementing the same notion of structure detection.)