When determining which operations to display for a multiple selection, use an intersection of the operations that apply to the members of that selection. The selection's context may add to or filter out the available operations or commands displayed to the user.
It is also possible to determine the effect of an operation for a multiple selection based upon a particular member of that selection. For example, when the user selects a set of graphic objects and chooses an alignment command, you can make the operation relative to a particular item identified in the selection.
Limit operations on a multiple selection to the scope of the selected objects. For example, deleting a selected word in one window should not delete selections in other windows (unless the windows are viewing the same selected objects).