Non-modal database system with methods for incremental maintenance

摘要

A database system with methodology providing "live" views of a database is described. In response to a user request (e.g., query) to display information from the database according to user-specified criteria, the system registers and displays a view (e.g., user-designed form and/or report); multiple views may be opened in this manner. In response to receiving one or more modifications to information stored in the database, the system employs incremental queries to maintain the "liveness" of the views. In particular, each registered view is notified of the modification (i.e., specific modified data records) and undertakes to apply the user-specified criteria for the particular view only against the modification. Here, the system determines for each view whether the modified data records should be added to the view (if such records now meet the user-supplied criteria for that particular view) or removed from the view (if such records no longer meet the user-supplied criteria for that particular view), without testing whether other records meet the user-specified criteria (i.e., without having to re- execute the query). In this fashion, the system maintains "live" views of the data so that all views reflects at all times the state of the underlying information or data, but without having to re-execute entire queries that initially gave rise to the views.