Despite the hype around ‘Event-Driven Architecture’ (EDA) over the past few years, I am confident that you will be unable to find a solid definition for ‘Event,’ on the web today. After an hour of research, the best definition I managed to find is one of several definitions provided by Red Hat: “We will define a software event as the immutable record that something happened within an application… Normally, events are broadcast to notify of change or replicate state across multiple applications.” Here, Red Hat are talking specifically about ‘Software Events’: each of which signals a ‘change of state’ in a particular ‘entity’ (e.g. Customer address changed) within a given distributed application.

This definition perhaps seems very straightforward, but what is not mentioned, is that there are in fact three different types of ‘Events’ according to today’s pundits: