Triggers vs. Polling

This is a trade-off decision.

Is the trigger load greater than the load would be if you polled every few minutes? If the database is getting hammered then the trigger load is likely higher than would be expected for polling at intervals.

How "real-time" do the alerts need to be? If you can wait five minutes or more then polling looks a little more attractive.

What is the project schedule like?  Seriously though, if you can take time out for quality, you can theoretically eliminate both. I haven't doen this yet but I have been thinking about it. If your application is using .NET or a similarly capable platform (Java should be able to handle it along with many other OO platforms) you could write a data access layer using a single-call type methodology where there is only one set of the classes instantiated at a time and all calls to update the DB are handled through this set of classes. That way you can perform the update and send a notification via event and/or delegate to any other classes that are tied to it. It sounds pretty complex but once you worked out the details I bet you could come up with a code generator that would build the classes for you (See my earlier post).