Event Based

I think the article could have given a formal definition of Implicit Invocation within the context of Event-based systems. Here is one I found from "An Introduction to Software Architecture" by David Garlan and Mary Shaw of Carnegie Mellon University:

"The idea behind implicit invocation is that instead of invoking a procedure directly, a component can announce (or broadcast) one or more events. Other components in the system can register an interest in an event by associating a procedure with the event. When the event is announced the system itself invokes all of the procedures that have been registered for the event. Thus an event 'implicitly' causes the invocation of procedures in other modules."

This paper http://www.mach-ii.com/resources/intro_to_implicit_invocation.pdf does a better job explaining the Event-based pattern although it doesn't explain how it could be used for parallelism. Also it says that Event-based is an Architectural Style, implying that it's not a pattern. It says that design pattern such as MVC implement architectural styles. So how do we draw the line between what's a pattern and what's an architectural style? I always thought architectural styles was a subset of patterns.