Paris. I have arrived a few hours ago to Paris, and I went for a walk in the streets to stretch my legs after the flight, my hotel is not far from the Bastille, so I went there and watched the monument that you can see in the picture and the people who watch it.. Now, returned to my hotel to check Email and rest, before my hosts are coming to take me to dinner.
Today's topic is a short reply to some discussion that actually event processing should be done as part of DBMS, this is not a new claim, it is repeating from time to time by one database person or the other; in my past I have dealt with active databases that has attempted to put some form of event processing functionality as part of a DBMS engine, overall this approach has not lead to a big traction on the DBMS products. The main idea has been to add some language constructs in form of ECA rules (that also support composite events) to DBMS engines. The only traction on products from this works is the notion of "trigger" that does not really to justice to what the active database community has tried to do...
Anyway, twenty years have passed and the event processing thinking has been evolved from the early thinking on active databases. As said the main issue here is not performance, as some of the vendors claims, but TCO. Many of what is called "complex event processing applications" deal with the detection of patterns over multiple event instances and types, SQL may not be a natural language to express such patterns, in some cases due to its set-oriented thinking and some other limitations. In fact, in some cases customer reported that they could save 75% of the cost of development time by using language that can express patterns more naturally. This difference may not be materialized in languages that are by themselves variations or extensions of SQL, but this is only part of the EP universe.
Of course, the DBMS community can return to the idea of active databases and add language constructs to express patterns in the DBMS engine, and I guess that this may be a valid variation of event processing, but it will not naturally blend into SQL, it will have to be an hybrid language. More about this - later.