In addition to invalidating cached results by time, I'd like the ability to invalidate cache based on an event. I think this is the moral equivalent of the existing functionality to reset a materialized view. I would like to scope the invalidation to particular tables or sets of tables. For example, suppose I cached the results of the following statements:
SELECT * FROM A
SELECT * FROM B
SELECT * FROM A,B

A call to invalidate A would invalidate the cached result sets from the first and third statements.