Question: Peter Buneman and Erik K. Clemons. "Efficiently Monitoring Relational Databases." ACM TODS 4, No. 3 (September 1979). This paper is concerned with the efficient implementation of triggered procedures (here called alerters)-in particular, with the problem of deciding when the trigger condition is satisfied, without necessarily evaluating that condition. It gives a method (an avoidance algorithm) for detecting updates that cannot possibly satisfy a given trigger condition; it also discusses a technique for reducing the processing overhead in the event that the avoid-ance algorithm fails. by evaluating the trigger condition for some small subset (a filter) of the total set of relevant tuples.