16. One or more tangible computer readable storage media comprising computer executable instructions which, when executed, cause a computer system to provide on a video output device a graphical user interface control for specifying a user-defined scope, said control exhibiting behavior comprising: (a) displaying a plurality of hierarchically arranged items, wherein each item of the plurality of hierarchically arranged items can be explicitly selected by a user for inclusion and exclusion from the scope, and wherein when the user explicitly selects an item for inclusion in or exclusion from the scope, the control implicitly selects all descendants of the explicitly selected item for inclusion in or exclusion from the scope, respectively, wherein each of the implicitly selected descendants can be deselected; (b) storing an indication of one or more explicitly selected items such that the one or more explicitly selected items can automatically revert to a previous state at a later time; and (c) displaying, separately from the plurality of hierarchically arranged items, a first list of selectable items explicitly included in the scope and a second list of selectable items explicitly excluded from the scope by the user, wherein each selectable item in the second list corresponds to a selectable item in the first list, and wherein when the user selects one of the selectable items within the first list of selectable items or the second list of selectable items, automatically navigating the plurality of hierarchically arranged items to display an item within the plurality of hierarchically arranged items that corresponds with the user-selected selectable item within the first list of selectable items or the second list of selectable items.
16. One or more tangible computer readable storage media comprising computer executable instructions which, when executed, cause a computer system to provide on a video output device a graphical user interface control for specifying a user-defined scope, said control exhibiting behavior comprising: (a) displaying a plurality of hierarchically arranged items, wherein each item of the plurality of hierarchically arranged items can be explicitly selected by a user for inclusion and exclusion from the scope, and wherein when the user explicitly selects an item for inclusion in or exclusion from the scope, the control implicitly selects all descendants of the explicitly selected item for inclusion in or exclusion from the scope, respectively, wherein each of the implicitly selected descendants can be deselected; (b) storing an indication of one or more explicitly selected items such that the one or more explicitly selected items can automatically revert to a previous state at a later time; and (c) displaying, separately from the plurality of hierarchically arranged items, a first list of selectable items explicitly included in the scope and a second list of selectable items explicitly excluded from the scope by the user, wherein each selectable item in the second list corresponds to a selectable item in the first list, and wherein when the user selects one of the selectable items within the first list of selectable items or the second list of selectable items, automatically navigating the plurality of hierarchically arranged items to display an item within the plurality of hierarchically arranged items that corresponds with the user-selected selectable item within the first list of selectable items or the second list of selectable items. 17. The computer readable media of claim 16 , wherein said control further exhibits behavior comprising: (d) when the user explicitly selects an unselected or implicitly excluded item: (i) changing a state of the explicitly selected unselected or implicitly excluded item to be explicitly included in the scope, and (ii) changing a state of each descendant of the explicitly selected unselected or implicitly excluded item to be implicitly included in the scope; (e) when the user explicitly selects an implicitly included item: (i) changing the state of the explicitly selected implicitly included item to be explicitly excluded from the scope, and (ii) changing the state of each descendant of the explicitly selected implicitly included item to be implicitly excluded from the scope.