col. 2, ln 20-41: Broadly, the present invention concerns an "active" calendar that automatically performs various user-defined tasks appropriate to calendar entries. Chiefly, the active calendar transmits user-defined messages in support of the calendar entries. The message may comprise internet search requests, e-mail messages, print requests, internal computer commands, or any other machinereadable message helpful to the user's calendar entry. As a more particular example, the calendar may analyze the user's calendar entries, search predefined sources for information related to the user's entries, filter the search results, and link the search results to the calendar entry, thereby aiding the user in his/her calendared activity. In advance of any calendar entries, the active calendar establishes a group of categories for use with calendar entries. Each category is associated with a particular planned event, such as shopping, teleconference, phone call, travel, meeting, child's activity, etc., and may be extended by the user. For each different category, there is a predetermined set of one or more subcategories. For a travel event, the associated subcategories may include source, destination, departure time, and arrival time. col. 6, ln 19-30: In addition to the various hardware embodiments described above, a different aspect of the invention concerns a method for operating an active calendar, which automatically performs various user-defined tasks appropriate to calendar entries. As one example, the calendar may analyze a user's calendar entries, search various sources for information related to the user's entries, filter the search results, and link the filtered information to the calendar entry, thereby aiding the user in his/her calendared activity. The active calendar may also automatically generate and transmit other machine-readable messages to destinations in support of the user's calendar entries. col. 7, ln 6-37: Referring to FIG. 4, one component is the calendar program 402, which comprises a calendar program that receives and records user submitted calendar entries describing planned events. The calendar program of the invention is configured, as discussed below, to associate each calendar entry with an event category and one or more subcategories. This may be performed independently, or with user assistance. Although the calendar program 402 may provide a thorough initial listing of event categories and subcategories, they may be extended to include additional event categories and/or subcategories defined by the user. As one example, the calendar program 402 may be based broadly on an application such as the LOTUS ORGANIZER program by IBM. The active calendar engine 404 is the heart of the active calendar system, and may advantageously be compatible with a variety of other existing calendar programs in addition to the calendar program 402. The engine 404 monitors the user's original entry and subsequent updates of calendar entries. On an appropriate basis or schedule, the engine 404 automatically initiates actions appropriate to the corresponding calendar entry. Chiefly, such actions involve sending machine-readable messages in support of the calendar entry. These actions, such as message sending, may be performed immediately, periodically, whenever a new entry is added or an existing entry updated, or according to another schedule. The engine 404 first consults the action rule database 414 (described below) regarding a particular calendar entry to determine which message format is appropriate to that entry, consults the action rule database 414 to determine the message content and destination, and then directs the sending of the message. col. 12, ln 28-44: As another example, the action rules database 414 may cause the event category "meeting" to result in searches for (1) each meeting participant's WWW home page, telephone numbers, and e-mail address, and (2) information concerning the meeting location, including address, driving directions, driving map, and telephone number. The search broker 408 may also consult a stored user-configured list to identify specific sources of information to use for each type of search. In the case of a search for information about a meeting participant, for example, the search broker 408 may be configured to search the user's personal address book 112, EUDORA e-mail recipient list 114, and the specific WWW search engines HOT BOT, YAHOO, and FOUR ONE. In the case of another event category, it may be appropriate to search through a different combination of Internet web pages, internal data 106, and/or direct link sources 122.