| 摘要 |
<p>To produce a continuous query for an append-only database, a client defined query first is converted into its minimal bounding monotone query if not already monotonic non-decreasing (hereinafter referred to as "monotonic increasing"). This monotonic query, in turn, is converted into an incremental query. The resulting monotonically increasing incremental query (Q') then is installed on the database as a stored procedure that takes two date/time parameters (hereinafter referred to as "time" parameters), one of which ( tau ) identifies the last time the procedure was executed, and the other of which (t) identifies the current time. All database records are timestamped as of the time that they are entered into the database. Thus, in operation, more or less standard procedure calls periodically invoke to each of the stored query procedures, thereby periodically executing the incremental queries over database records that have timestamps spanning successive time slots. <IMAGE></p> |
